In either case, it is real, it is tangible, and it cannot be denied. The physical evidence never lies. It is what it is, although we can certainly misinterpret its meaning. That failure, however, is still human in origin; the fault does not lie with the evidence. Whether it is the ambiguity of the involved. Properly considered, the physical evidence establishes a framework of facts that are irrefutable by anyone. This framework will serve as a reference to which the investigator can compare the testimonial evidence, allowing him or her, in many instances, to corroborate or refute the information presented.
When the investigation becomes mired in subjective information, this objective framework will be a ready reference to return to for clarity. Together, the physical evidence and any testimonial evidence that ultimately stands the test of time will allow some level of insight into the overall event. However, the concept of physical evidence involves more than the mere collection of things. Each scene encountered tells a story. Thus a complete consideration of physical evidence demands that investigators be critically observant. The information available in these simple on-scene observations can be significant.
The Interpretive Value of Evidence The value of an item of evidence is not based solely on its mere presence in the crime scene. Crime scene analysis demands that the investigator consider the interpretive value of the evidence. Crime scenes are often likened to a jigsaw puzzle. The police arrive at a scene generally devoid of answers but containing numerous artifacts. Each artifact is, in effect, a piece of a puzzle. Unfortunately, the police do not have all of the pieces to the puzzle, nor do they have the luxury of referring to a picture on the box containing the puzzle pieces.
The crime scene technician is left to ponder innumerable questions regarding the scene. For instance, is a given artifact part of the puzzle to be solved, or is it perhaps related to some event that occurred hours or days before? Just as the addition of each piece to a jigsaw puzzle brings clarity to the overall picture, the consideration of each artifact in the scene brings knowledge to the event being investigated. Merely owning the pieces of the puzzle is not enough. The investigator must be able to place the pieces in the overall picture.
For example, the presence at the crime scene of a bloody shoe mark that is identified to some specific individual is significant. The ability to distinguish that shoe mark as having been made at or near the time of a beating by evaluating the disturbed spatter beneath the shoe mark is of far greater value. In the same fashion, the physical location of the shoe mark in the scene, which perhaps contradicts an explanation offered as to why the shoe mark is there, is of equally important value. This aspect of context and the interrelationship of evidence to the scene and other items is a major reason why the crime scene technician documents the scene through sketches and photographs.
Lacking the ability to functionally place an item of evidence back into the scene, the value of these interrelationships would be lost. Case Example: Scene Context and Interrelationships A husband returned home in the middle of the day and discovered his wife beaten to death. Overwrought, he claimed to have begun attempts at CPR and immediately notified the police. EMS emergency medical service technicians arrived moments after the call and found him on the floor, bloodied from top to bottom. The scene investigation and subsequent autopsy indicated that the woman was bludgeoned with an object that had distinct angled corners.
Despite significant effort to locate anything remotely similar, the police failed to find such an object at the scene. They certainly failed to locate anything similar that was bloodied. In the examination of the dress shirt worn by the husband, a number of odd bloody pattern transfers were located, as seen in Figure 1. The angles and edges of this unknown item had similar dimensions to the angles and edges evident in the pattern of injury on the victim.
The bloody pattern transfer, however, was a positive and not a negative, so contact with the injury itself could not explain its creation. The husband claimed that the pattern transfer was simply a bloody mark caused by his actions while performing first aid. Although the husband could present reasonable explanations for being bloody, the pattern transfer was a major contradiction.
The police arrived on the scene while he was still inside, nothing was removed from the scene, and they certainly did not overlook a bloody weapon. The husband was alone, claimed to have come home alone, and made no claim of having left the scene for any reason. So nothing could have left the scene between the time the police were notified and their arrival. The mere fact that the husband was bloodied was certainly expected and arguably explained in a variety of ways. But the fact that he was bloodied by something that was no longer present in the scene was significant, because no explanation offered could clear up this contradiction.
He claims not to have left or altered the scene and to have been alone in the scene. Yet the bloody object is not present in the scene. If he is truthful, this demands that someone else altered the scene. But that also demands that the husband was present in the scene before the alteration. His story cannot explain this contradiction. The husband being bloody was not an issue until it was examined in light of the scene context. In the crime scene, context is everything. It is only through context that we derive conclusions.
Forensic lab analysis may define specific facts about an item of evidence, but that can only tell us part of the story. Possession of data is meaningless unless we put it to work and look beyond the tree to see the forest. In considering this context of the evidence, Chisum and Rynearson offered that such context can manifest itself in a number of ways.
Predictable effects Unpredictable effects Transitory effects Relational detail Functional detail2. Predictable effects are those changes to the scene or evidence that occur with some rhythm or regularity. Based upon this regularity, such evidence provides the investigator a factual reference or, at the very least, an inference as to the actual time of the crime. Classic examples of predictable effects are found in forensic entomology, in which the stage of insect activity at a homicide scene allows the entomologist to establish the approximate period since death. Other examples include the onset of rigor and livor mortis in the body, which in a stable environment follows regular and somewhat predictable timelines following death.
Unpredictable effects are changes that occur in an unexpected or random fashion. Unpredictable effects alter the original scene and the evidence. If unrecognized, such effects can cause significant misinterpretation of the scene. A classic example of an unpredictable effect is found in the entry of police or EMS into a crime scene. Oftentimes they open doors or turn on lights and then fail to report such actions. The subsequent observation by the crime scene technicians of these post-incident changes often results in incorrect premises regarding when the crime occurred or the manner of entry or exit by the perpetrator.
As Chisum and Rynearson commented, such changes can be disastrous to the overall investigation, as the original context of the evidence is lost forever. Transitory effects manifest themselves at the crime scene in a number of ways. Oftentimes they are fleeting. Unlike the body, the gun, or the bloodstains, transitory effects fail to stand out to the investigator. It is only through deliberate observation that transitory effects are noted.
Examples of transitory effects include the heat of a burning or burnt cigar or cigarette, the presence of ice in a glass, or odors of chemicals or colognes that are present when the first officer arrives. A technological example of a transitory effect is the heat signature of a tire on a roadway. When evaluating significant crashes or fatality accidents, a handheld thermal imaging device allows the crime scene technician to differentiate new and old tire marks on a roadway.
Ultimately, time and environment will destroy any transitory effects present in the scene. Failures to observe, smell, or feel such evidence in the early stages of the scene will result in the loss of such information. Many of the actions and. Examples of relational details would include the presence of a void pattern on a wall surrounded by spatter, a clustering of shell casings on grass, the presence of a weapon in close proximity to the victim, the recognition that a gunshot wound is distant vs.
Through relational details, the investigator is able to establish a correlation between various objects. Significant in our understanding of relational detail is the belief that the item was actually at a given location at the time of the event. Those arriving at the scene or those processing the scene often displace easily moved items, changing and destroying the relational information. In an exterior crime scene, the position of small items can be changed as a result of wind, rain, or water flow. The crime scene sketch and associated measurements allow the scene investigator to document these relational details.
It is rare that the scene processor will recognize every relational aspect that may subsequently be at issue during trial. This is one reason that the measurement and fixing methods such as triangulation and baseline techniques should be applied to all items of evidence, not just those the scene processors think are important at the time. These measurements are often seen as laborious and unnecessary, but without them, information to prove or disprove a relational detail may be lost. Functional details manifest themselves in the operating condition of items in the scene.
Is the weapon capable of operating in a normal fashion? Was the clock alarm set for a specific time? Did the deadbolt operate normally? All of these are functional details. Each tells the investigator something about what was possible or impossible given that specific item. Functional details assist the investigation in a variety of ways. They can disprove specific allegations e. The author, along with Bevel, offered an additional approach to evidence observations when discussing crime scene reconstruction.
What is it? What function did it serve? What relationship does it have to any other items of evidence or to the scene itself? What does it tell us about timing and sequencing aspects? How an item is used in the scene is not always congruent with what the item actually is or what it was designed to do. Just as important, recognizing the nature of the item will assist the investigator later when he or she begins looking at relationships and decides whether the item is foreign to the scene.
Knowing this prevents the investigator from wasting investigative effort at some future point. The first consideration then is to identify the item, if possible, and consider its use, function, or purpose in the scene. Consider the example of an empty wax paper roll that is found in the kitchen area of a suspicious fire. A wax paper roll in a kitchen is not unexpected. This is certainly an item one would find in many kitchens. Is it merely a pre-incident artifact left by the kitchen owner? That is. Figure 1. If true, the item lacks evidentiary value and will likely be left without further examination or processing for fingerprints.
The nature of this residue is such that it might easily be overlooked. The consideration of the wax paper as an arson trailer and any subsequent effort to resolve the issue may result in locating additional evidence. Most crime scene investigators have heard of or seen the forensic linkage triangle in one form or another Figure 1. The function of the forensic evidence linkage triangle is to remind the investigator that each item discovered must be considered a mechanism for linking the scene, the victim, or the suspect in some form or fashion.
Ultimately, every piece of evidence is considered against this concept to determine whether any links exist and if they are of evidentiary value. The nature of these links may or may not serve to illuminate investigative issues. This is particularly true in our consideration of trace evidence.
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Both had access to the home and routinely interacted with each other; therefore transference of fibers would be an expectation. Every item of evidence must be considered to see if some link between the three entities is possible. If the links exist, the investigator must then consider whether it has evidentiary value or is explainable through some other innocent mechanism.
After considering relational issues, the last question deals with timing and sequencing aspects. Timing and sequencing are two distinct concepts. Timing aspects allow us to place the time of the crime in some form or fashion. Sequencing aspects help the investigator decide in what order the crime occurred. Some classic examples of timing aspects at a crime scene are meals that are in preparation or completed; the condition of stomach contents of homicide victims; and alarms, clocks, or timers that are set but have yet to go off.
The pathologist will often provide significant timing aspects through the consideration of body temperature or the evident stages of livor and rigor mortis. All of this evidence suggests the relative or actual time of the crime. Sequencing aspects tell the investigator in what order certain events occurred as the crime proceeded. Crimes are not instantaneous events. Criminals must approach the scene, act within the scene, and then depart. The consideration of the various items of evidence will lead to a definition of what are often referred to as time snapshots of the crime: specific moments when specific actions occurred.
One of the most critical elements of crime scene analysis is the process of logically ordering these snapshots in order to understand how the events proceeded. It is sequencing information that allows the investigator to do this. Sequencing information can present itself in almost any format. Examples of sequencing information include the disturbance of a bloodstain pattern by a shoe mark or handprint, the order in which a series of items are layered on the floor, or the manner in which radial cracks emanate from a series of bullet holes in pane glass.
Each example allows the investigator to understand the order in which specific events occurred. By considering all of the sequencing information, the crime scene investigator is able to objectively sequence a majority of the actions composing the crime. Together, timing and sequencing aspects provide significant information to the criminal investigation, and neither type of information should be overlooked. Each of the approaches described allow investigators to evaluate the evidence and information they find within the scene. What relationship does it have? What does it tell us about timing and sequencing?
Crime scene technicians cannot simply be garbage collectors. They must know what they are looking for, and they must understand what each piece of the puzzle tells them. As important as it is to the job to understand what we are looking for in the crime scene, it is equally important to understand what we are trying to prevent from occurring while at the crime scene. Good Crime Scene Examinations and Scene Integrity Issues Every action taken in the crime scene has some level of destructive effect on the scene.
This is a given and something that cannot be escaped. Scene degradation occurs from the moment the crime begins and continues until the last officer turns off the lights and leaves the scene. Actions of suspects, witnesses, the first responding officers, EMS, the environment, and certainly those of the crime scene processor will result in the disturbance and alteration of the scene. Given this understanding of the inevitability of scene alteration, the basic goal of any processing methodology is to limit the damage and recover as much evidence and context from the scene as possible.
No one has yet defined the one and only right way to process a crime scene, but any good processing methodology will demand the following five basic ingredients:. First and foremost, those responsible for examining the crime scene must understand what they are trying to accomplish. Knowledge on the part of the crime scene investigator is critical. As previously discussed, the scene processor is more than just a collector of things; the investigator must seek the interpretive value of the evidence. By understanding what he or she is looking for, what the lab can do with the evidence, and what questions should be asked, the investigator will not overlook information and evidence.
The weakest link in forensic science lies with the crime scene investigator. Investigators do not need to be experts in every forensic science, but they must understand the nature of the different types of forensic evidence they may encounter in a scene and how that evidence must be collected and preserved to be of value. Beyond knowledge, the processor must also have the skills and tools required to recover evidence. Examples of skills and tools that may be necessary include competency with the available camera equipment, the ability to conduct fingerprint recovery under a variety of conditions, or the casting of various impressions.
The situation involved a young woman who had been shot once in the head producing a perforating wound. The bullet passed from the left side of her temple, out the opposite temple, and into a couch cushion. Investigators were unconvinced of the story told by her boyfriend of a self-inflicted injury. They had trajectory rods available to them and proceeded to use them to demonstrate the path of the bullet.
As the figure demonstrates, they violated two basic rules in analyzing wound paths and trajectories. First and foremost, they introduced a rod into a wound at the scene. This violates pretty much every standard of practice known today. The introduction of the rod into a wound has significant potential to create its own path, particularly through macerated brain, rather than following a bullet wound path.
The two holes in the skull certainly provide two known reference points, but even at the morgue this behavior is generally considered bad practice. This relationship can be better demonstrated through demonstrative evidence at a later date, using the defect positions as defined by the medical examiner. The second mistake becomes evident where the rod intersects the couch cushion.
The cushion is a pliable surface and given an approximately 8-pound weight pushing down and slightly forward against the rod, the cushion can be seen bunching up. The trajectory defined by the path of the bullet through the cushion, which was probative, is deflected by the weight of the head against the rod and the photograph is unreliable as a true trajectory. Simply put, in the wrong hands even good tools and equipment can make for bad practice.
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The second mistake was not recognizing that the rod in the cushion was deflected by the head and did not demonstrate the true trajectory. Crime scene equipment must be maintained and its proper use understood by the crime scene investigator. Otherwise these tools amount to nothing more than expensive junk.
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An additional consideration is that whatever approach is used to process the scene must be methodical. To be methodical, the method must be all-encompassing and purposefully regular. Without a methodical approach, steps are often forgotten or overlooked. Some processors find the use of investigative checklists a functional means of maintaining this regularity. Therefore, the scene investigator must maintain a level of flexibility in dealing with each new scene.
Flexibility on the part of the investigator is critical. Each scene is unique and presents its own challenges. The investigator will have to make hard decisions when presented with fragile evidence or competing or contradicting interests. For example, basic crime scene methodology tells us that we should photograph the entire scene before collecting evidence. But what if the evidence is a shoe mark in the soil outside a burglary homicide, and the investigator realizes a storm is moments from breaking?
If a downpour occurs, the evidence will be destroyed, so the investigator must act promptly to preserve or collect the mark before that happens. The investigator must always recognize when it is necessary to break from routine in order to achieve the desired end result. It lay supine in a snow bank, with portions of the head showing above the snow. As normal excavation techniques progressed, immediate investigative concerns were noted due to the fact that a blood flow was observed moving up the nose of the victim. The final position of the victim was clearly not the only position of the victim subsequent to wounding.
The initial. With obvious concern as to the likely movement of the body after wounding suggesting a dump site or subsequent scene alteration , processing continued. When all the snow had been removed, it was apparent that the body would not be easily recovered. This layer encased the entire body and clothing, and it was 4 to 6 in.
Following several hours of effort using the heaters, as well as attempts to chisel around the body, the investigators were no closer to freeing the body than they were before. The heater was damaging the clothing on the body to the point of burning small sections that were exposed too long. As evening fell and the temperature dropped, it was clear that some extraordinary method was needed. Part of the overall problem lay in the fact that the body itself was a block of ice, frozen solid by long-term subarctic exposure.
The crime scene investigators, partly out of studying the situation and partly out of desperation, chipped a deep hole along the high side of the body, large enough to insert a long-handled 2-in. The blade of the pick was then forced into this hole, and outward leverage was applied to the handle. To say the least, a number of raised eyebrows were observed, and guffaws heard as the technique was applied. Where the body had refused to budge through all the prior attempts, in a matter of seconds a slight pop was heard.
The body popped from the grip of the ice, intact and none the worse given the odd method of retrieval. Nevertheless, some action must be taken, and the crime scene investigator cannot be afraid to take a calculated risk. Flexibility in practice allows the investigator to see through the problem and find a solution. Last but certainly not the least of the necessary ingredients for a good scene examination is the need for coordinated effort. A scene examination conducted without coordinated effort is unlikely to achieve the desired result.
Coordination ensures that all actions are taken in the proper order and that important aspects of the scene examination are not sacrificed without prior consideration. If the investigator is to achieve the goal of crime scene processing, which is the collection of the evidence and scene context in as pristine a condition as is possible, then these five basic ingredients of good scene examination practice must be combined with an understanding of basic scene integrity concerns. Addition of material results in what are referred to as post-incident artifacts.
In effect, the authorities end up creating evidence that was not there to begin with.
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Examples run the gamut of shoe marks to blood trails. Officers, EMS technicians, supervisors, almost anyone can end up adding artifacts to a scene. Individuals walking in from a wet exterior may leave shoe marks on floors and carpets, intermixing with the shoe marks of concern. EMS or first responders who attempt first aid often create blood trails and bloodstain patterns through their manipulation of the body. Hours into a late-night crime scene, it would be unusual not to observe coffee cups that were not there before processing began.
The addition of material is always a concern. Every contact does leave a trace. At the very minimum, the crime scene investigator must distinguish between those items that are post-incident artifacts and those that are actual evidence related to the event. It is this consideration that requires the responding officers and investigators to ask and determine who did what to the scene prior to their arrival.
Later chapters will discuss isolating the scene and establishing collection points for evidence and equipment, all of which are directed at preventing the addition of material. There are numerous examples of the destruction of evidence. Officers arriving at a burglary scene early in the morning are likely to encounter a dew trail caused by the approach or departure of the subject. By the time the investigator arrives, it is unlikely this dew trail will remain, having been trampled by well-meaning officers searching the area. A classic example of destruction occurs when a homicide victim is placed into the body bag.
Prior to this action, there are often bloodstain patterns on the clothing or exposed skin surfaces. During transport in the body bag, residual bleeding occurs, which contaminates the body bag itself. As a result, saturation and contact stains end up on the clothing and victim, obscuring forever the original patterns of interest. Another example of destruction occurs when, by focusing too quickly on the primary scene, investigators miss evidence on the periphery. As additional resources arrive in the form of more people and vehicles, this peripheral evidence is trampled and lost.
Many of the investigative beliefs on how and when to deal with fragile evidence, as well as the necessity of using an established methodology, are directed at preventing the destruction of material in the scene. Movement of material is the last scene integrity issue. In effect, movement of material significantly changes the relational aspects observed by the crime scene investigator. A classic example of movement of material occurs when an officer encounters a weapon.
SWAT officers often demonstrate a special penchant for kicking weapons from the hand of a suspect, despite the apparent fact that the suspect is dead. Consequently, by the time the investigators arrive, the weapon is 15 ft from the suspect. If no one takes responsibility for this action, it leaves open the argument that the suspect was shot after giving up and putting down the weapon. Similarly, patrol officers have been known to take a suicide weapon from the vicinity of the body and place it on the opposite side of the room.
The investigator arrives and, without recognizing this change, perceives what was a suicide as a likely homicide. The opening of doors, the opening and closing of window shades, the. It is not uncommon in the photographic documentation of a crime scene to observe a single item in various locations. Counsel will use these contradictory photographs to challenge the appropriateness of the crime scene processing or to claim that the resulting false relational links prove some alternative theory.
The arrival of police and the haphazard processing of the scene create many of these unnecessary movement actions. Each unrecognized movement creates false relational links. The crime scene investigator must know when these changes were made, by whom, and for what reason. This position was clearly a posthomicide act by the perpetrator. Oddly enough there was a small piece of clothing that was neatly folded and placed across the vaginal area. Given the disarray of the scene and the disrespect shown to the victim subsequent to her death, this item made no sense in the overall picture.
While interviewing the first responding officers, one of the younger officers admitted his role in altering the scene prior to the arrival of investigators. He felt it his duty to offer her, in death, some modicum of modesty. Therefore he chose to place the clothing over her crotch before the world arrived and saw her as he had found her.
In his eyes it was only proper and appropriate that she be given this respect. It is often a specific action taken by a responder at the scene that changes the scene. As in this example, the change may not have been necessary, yet it did occur. The crime scene investigator always seeks to identify and understand why these changes happen.
By understanding the three scene integrity issues as they relate to the techniques and approaches of scene processing, and by applying the five basic ingredients to good scene examination, the crime scene investigator is more apt to make good, defensible decisions when faced with difficult choices at the scene. This is done in an effort to define who did what, and why. The crime scene is clearly a source of significant information in this pursuit, and the crime scene technician or crime scene investigator is likely to remain actively involved in any future trial associated with the event investigated.
How does the investigator maintain objectivity and remain true to the profession throughout the search for justice? First and foremost, it is important to understand that the investigator has no personal stake in what he or she finds in the scene. I cannot change it. Until we look, we do not know what we will find. Once we find it, we cannot ignore it simply because we do not like what it tells us. But more importantly, the crime scene investigator really should not care what he or she might find.
If the goal is truth, then how that truth plays out is of little consequence to the investigator. Sure, investigators will all have pet theories and suspicions, but if they are true to their profession, then they will remain open and objective, certainly willing to consider new evidence. Investigators must report their findings objectively and truthfully to whomever needs to know, no matter how those facts impact on their personal beliefs.
This is a function of justice, not law enforcement. The job of law enforcement has always been to bring people to justice. The nuances between these two statements, although perhaps minor in form, are major in context. The failure of police to recognize those differences often leads to significant failures in the justice system. Will investigators believe in the guilt or innocence of the individuals they investigate? One would hope so. Belief in the involvement of some individual in a crime is not a bad thing, so long as that certainty does not cause the investigator to sway from procedures or alter testimony.
The author was once involved in a case in which an alleged police expert argued that the police had only the responsibility to investigate a crime to the standard of probable cause. It is important to note that probable cause is not the investigative standard. That is the standard of the court, so why would we pursue anything less? Truth is only achieved through detailed study and analysis. Investigators may not achieve that standard in every investigation, simply because they lack specific evidence to really know everything they want to know. Nevertheless, it must remain the standard they pursue.
The investigator will never have every piece of the investigative puzzle. To prevent that lack of knowledge from affecting their role in the criminal justice system, investigators must follow good investigative ethics. Such investigative ethics demand that investigators collect and document the evidence as they find it. The investigator cannot pick and choose what to report.
Just because a particular item of evidence does not conveniently fit into the pet theory of the hour does not mean that it is unimportant or unrelated. This is a particular concern in the early stages of the investigation, when many initial subjective theories abound. Investigators must consider all viable theories until they are excluded. They cannot proceed with tunnel vision. Excluding an alternative theory, such as one supported by an alibi, may work out fine in the early stages of the investigation, when no one is there to challenge the investigator.
Sooner or later, however, someone—most likely a defense counselor—will force the investigator to consider those alternative theories. The wrong time to deal with and rationally argue for or against such a theory is while testifying at trial. The investigator should have considered whether a theory or alibi is viable long before the state enters into trial.
If the crime scene investigator is truly objective, there will be few if any alternative theories presented by counsel that have not been taken into consideration. Granted, that will not prevent counsel from raising issues, but the investigator cannot effectively argue such theories for the first time while sitting in the witness chair. The environment of a courtroom is far too emotional and far too antagonistic for on-the-spot objective evaluation. Another critical aspect of investigative ethics is the need to treat all facts the same.
The investigator cannot differentiate in how he or she documents the information obtained. It is rare that there is not some form of exculpatory information present in the crime scene, something that suggests someone other than a particular suspect is responsible. These contradictions are expected and they are nothing to be afraid of. Investigators must report exculpatory information and not subjectively exclude it from their report.
Once again, investigators do not know what the scene will tell them, and they have no personal stake in what the evidence ultimately says. So nothing defined by the scene is bad. The last consideration of investigative ethics is that investigators can never let any lawyer, defense or prosecution, tell them what they know.
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Investigators must factually and objectively report the information that they have obtained. How the lawyers choose to use the information is their business, but they do not get to define what the investigator knows or what he or she has found. Unfortunately, the fact is that this message must be made, and it is a message that we must make again and again at every level of law enforcement. Perhaps as a result of some warped sense of duty or out of sheer frustration and disillusionment with a justice system that seems to make no sense at times, crime scene investigators and analysts have altered evidence, manufactured evidence, and failed to testify truthfully.
Although still rare, these failures call in question the integrity of every single law enforcement officer. As a result, even an honest mistake becomes the fodder of conspiracy theories by lawyers out to make a buck through civil suits or groups out to further some agenda. Our fears over the inhumanity we see day to day and our desire to stop it, and the ever-growing chasm between law enforcement and the citizens we serve, may have indirectly affected our beliefs.
Despite the confusion, despite the chaos of our system, and despite the personal dilemmas we face daily, investigators must always remember that small integrity and objectivity failures will ultimately lead to larger integrity and objectivity failures. It can never be stated too loudly or too often that investigators must remain objective and true to their profession. Summary The system of justice may be convoluted, but the role of the crime scene investigator in that system is straightforward. The investigator seeks to establish the truth regarding a given event or crime by objectively pursuing this truth without regard to any other agenda.
Truth is defined by the collection of evidence, factual information that allows us to draw some conclusion about an event. The crime scene investigator realizes the significance of physical evidence in defining this truth. Unlike testimonial evidence, physical evidence does not lie.
We as humans may well misinterpret what the physical evidence is telling us, but that is our own fault. Physical evidence will aid both the investigator and the jury in corroborating or refuting much of the testimonial evidence. Used properly, physical evidence establishes a foundation of objective information that few, if any, can refute. To understand why investigators take the steps they do in collecting this physical evidence, one must understand the underlying conceptual ideas behind crime scene investigation.
Oftentimes the investigator is faced with competing interests and difficult choices. Whatever action he or she takes must be defensible in court. It is not enough to have taken the action; the investigator must articulate why. Understanding these principles allows the investigator to make difficult decisions when faced with contradicting requirements.
The collection of items at the scene, the mere ownership of physical evidence, is not the end-all of crime scene processing. The crime scene investigator must realize the interpretive value of evidence, which depends on the context in which the evidence is found. This context is manifest in five effects or details: predictable effects, unpredictable effects, transitory effects, relational details, and functional details. In pursuing this context or the interpretive value of the evidence, the investigator must also ask several questions about each item of evidence found.
What is this item and how was it used? What relational links will this item establish between the scene, the subject, and the victim? In what way will this item define the time of the crime or sequence the actions associated with the crime? Once again, by looking at more than mere content and by considering the context in which the evidence is found, the investigator will find that far more information is available in seeking the truth of the matter.
There is no one right way to process a crime scene. When evaluating methods, the investigator must consider that any good processing methodology will include five key ingredients. These are knowledge on the part of the investigator, the skills and ability to accomplish what the knowledge defines must be done, and a methodical approach that defines in what order it will be done.
Flexibility, or the ability to adapt to the requirements of a given crime scene, is another key ingredient. The fifth ingredient is the need for coordinated methods, where the efforts of all participants mesh to maximize the information extracted from the crime scene. When these five ingredients are combined with an understanding of the three scene integrity issues, the investigator can functionally and reasonably choose between different courses of action at the scene.
The investigator knows that his or her methods must prevent, whenever possible, the addition of material into the crime scene, the destruction of material in the scene, and the. Finally, with all of these issues in mind, the investigator recognizes the need to have a strong sense of ethics. Crime scene work often presents significant personal ethical dilemmas. Investigators must never allow such issues and their associated dilemmas to cause them to stray from their professional duty, which is to remain an objective seeker of truth.
Suggested Reading Bevel, T. Chisum, W. Gardner, R. Nordby, J. Chapter Questions 1. What is the basic goal of crime scene processing? The police utilize five basic objectives in seeking their goals of preventing crime and disorder and protecting the life and liberty of their fellow citizens. Which two of the five objectives are more closely related to the crime scene investigation and why?
Why is physical evidence more objective than testimonial evidence such as eyewitness accounts? The interpretive value of evidence is a function of what? Chisum and Rynearson identified five ways in which context manifests itself in the crime scene. What are they? Bevel and Gardner defined four questions that the investigator should ask about evidence.
Describe and explain the forensic linkage triangle. Any good crime scene examination requires five key ingredients. Describe and explain the three crime scene integrity issues that the investigator considers. What is the standard that the investigator uses when pursuing a solution to crime, and why is this standard necessary?
Notes 1. Bevel, T. Geberth, V. Saferstein, R. Throughout this text, one particular theme will be evident: physical evidence has greater power and ability than testimonial evidence in defining what happened at any crime. This is not to say that testimonial evidence should be ignored or excluded, but an understanding of physical evidence will provide an objective foundation for any subsequent theory of the crime.
Physical evidence is what it is, and it is tangible. Presented with DNA deoxyribonucleic acid evidence from the scene or a photograph of the condition of the scene, only a fool would argue that the DNA was not really there or that the scene looked other than as depicted in the photograph. To gauge testimonial evidence, all we have is our perception of the individual. Does she appear honest? Did he have the ability to perceive what he reported? Any witness is capable of unconsciously misperceiving events or, for that matter, purposely misrepresenting events based upon some personal agenda.
This is a well-established fact in the study of criminal investigation. Understanding this, we do not exclude testimonial evidence, but we certainly seek corroboration of testimonial evidence through some objective means. That means is called crime scene analysis, which is the end result of any effort directed at crime scene processing. The more physical evidence recovered, the more likely a functional and objective theory of what transpired during the crime will be forthcoming. In , Luke S. In the past, that was a relatively easy process.
Items such as fingerprints, bloodstains, shell casings, or weapons stood out at the scene, leaving little doubt that they might serve a function in solving the crime. But with each new advent in technology, the capability of forensic science increases. Now, even the slightest trace of evidence e. Before the crime scene technician can expect to process a scene for evidence, he or she must have a working knowledge of the nature of physical evidence, what a crime lab can do with it, and how best to collect it.
This in no way presupposes that he or she is expert in every discipline of forensics; lacking this understanding, the technician is likely to overlook evidence or collect it in an inappropriate fashion. If the crime scene investigator fails to collect the evidence, or collects it in an inappropriate fashion, the laboratory scientist cannot do his or her job.
Therefore, it is incumbent in the job for the crime scene technician to take an interest in all aspects of forensics and to try to remain current. An effective means of accomplishing this is to get involved in the various professional forensic associations and to pursue certifications like those offered by the International Association of Identification.
Class and Individual Characteristics Not all evidence is created equal.
Some evidence provides specific and detailed information for the investigation, while other evidence provides only limited assistance. Based on specificity, the characteristics presented by all physical evidence can be classified in two categories: class characteristics or individual characteristics. Class characteristics describe traits or characteristics of evidence that allow the item to be compared with a group.
Depending upon the similarities or differences of the class characteristics, items can often be excluded as belonging to a group. Class characteristics may include size, color, common manufacturing patterns, or taxonomic classifications. By comparing the class characteristics of a questioned item to a known item, should any one of the class characteristics fail to match, the forensic scientist can effectively establish that they are not of common origin. The color and refractive index the manner in which the glass bends light can be compared with a sample of known glass from the crime scene.
If the forensic scientist discovers that either characteristic does not match, then he or she has effectively established that the two items are not of common origin. On the other hand, if both characteristics match, that does not prove the items are of common origin. In that instance, they simply cannot be excluded as having come from a common origin.
In other words, it is possible that the suspect glass came from the scene, but it is also possible it came from some other broken glass somewhere totally unrelated to the scene. Class characteristic evidence is routinely presented in court, but it must always be properly represented. Class characteristic evidence is also widely used as a screening mechanism by the forensic scientist. For example, if screening of a blood sample finds a specific antigen a class characteristic in the known sample but this antigen is absent in the questioned sample, then the two samples are excluded as having a common origin.
The exclusion is objectively established between the two samples, and there is no need to pursue an expensive and time-consuming DNA examination. Individual characteristics make up the second category. Individual characteristics allow the forensic scientist to compare the item with a specific object or person and include or exclude it as having originated from that object or person.
Fingerprints result from natural variation in human beings, and no two fingerprints are the same. Presented with a fingerprint in the crime scene that is compared with a known fingerprint of an individual, the fingerprint examiner will either include or exclude the individual as having left the print. There is no in between, no gray area. This latter situation is an inconclusive result due to having insufficient detail to make the comparison. Individualization, the examination of individual characteristics, is a major goal of forensics.
It is powerful evidence to conclusively state that this blood or this fingerprint came from this individual. Of course, the power of this evidence is directly related to the context in which the crime scene technician finds it. Evidence considered outside of. For instance, DNA is often touted in the press as a panacea for crime solution, and it is certainly effective evidence. But the presence of matching DNA alone does not prove a crime. If it did, then every male in the world should shake in fear at the possibility that his lover might become the victim of a sexual murder and his DNA might be discovered on the body.
If the mere presence of DNA establishes a crime, then we may as well send the juries home and start rounding up all the husbands and lovers. No matter what evidence is available, no matter what its characteristics, it is only by considering all evidence and the context in which it is located that solutions to crime are found. Thus every piece of available evidence in a scene has function, and the crime scene technician cannot afford to haphazardly collect or preserve it. The list of forensic disciplines is a long one, including everything from forensic anthropology to forensic toxicology.
This chapter considers some of the more common forms of physical evidence discovered at the crime scene and evaluated by the forensic scientist, including fingerprint evidence, serological and biological evidence, trace evidence, firearms evidence, tool mark evidence, shoe and tire impression evidence, document evidence, general chemical evidence, and computer forensics. For further insight, there are a number of texts available that deal with the full scope and specific processes used in all of these forensic disciplines. Edmund Locard, a French criminologist, is considered by many to be the father of the modern crime laboratory.
Locard believed that whenever two objects came in contact with one another, material from the first would be transferred to the second, and material from the second would be transferred to the first. This principle is the underlying theory behind trace evidence examination. It is directly applicable to our actions in crime scene processing and the theories underlying crime scene analysis. One has to wonder if Professor Locard truly understood just how correct he was.
Would he be surprised by our modern ability to find DNA in minute quantities? Given the technology revolution, the true question in forensics today is: How far will technology go in allowing us to recognize these contact traces? It is particularly problematic in trace evidence examinations and serology examinations.
By exposing one item of evidence to another, evidence from the first is passed to the second, and vice versa. Consider the following example. In collecting rape evidence, the investigator often deals with the victim in the blind, not knowing at first why she is there or what she will say. In many instances, the victim identifies a perpetrator within a short period, and the investigator may talk to a suspect on the same day. If the investigator were to set the victim in a particular chair prior to collecting her clothing, a transfer of fibers from the clothes to the chair would occur.
This is cross-contamination. It is the responsibility of the crime scene technician to isolate evidence and use validated collection techniques to prevent cross-contamination issues. The unique damage of the metal razor blade shown in this photograph and the position of the staining on both sides of the break produce a form of mechanical fit.
Mechanical fit is where an item is damaged and pieces are deposited in the scene. These pieces, when collected, are preserved in their original shape and condition. When the source object is located and examined, it may be possible to see exactly where the piece broke off from the original object see Figure 2. Because the breakage is accidental, it is also random, which makes it possible to individualize a specific piece to a specific item.
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