Experience becomes the best teacher as to what items will have the most relevance for the investigation of each type of crime. At the crime scene, the perpetrator may leave traces that may be visible or invisible 3.
When securing the scene, care should be taken not to destroy or alter the tracks or to create new ones. Traces can appear as papillary prints, footprints, traces of fibers from clothing, traces of blood, traces of teeth if the offender consumed food at the scene.
During the course of the examination, it is necessary to inspect the vicinity of the scene, as there is a possibility that the perpetrator, upon arriving at and leaving the crime scene after the burglary, left traces to identify him or indicate his movement, hid the stolen objects or discarded used tools. Saliva is sprayed, hair is yanked from its roots, skin is scraped off, and flesh is torn 1.
Violent crime inevitably leaves a number of different types of biological materials behind as witness to the attack. With the possible exception of semen in the case of sexual assault, no type of biological fluid or tissue is consistently more revealing about the victim, the attacker, and the circumstances of the assault than blood.
Blood can yield DNA that identifies the crime's participants. Its splash patterns can reveal the site and mode of the attack. Blood can make an attacker's fingerprints or shoeprints readily visible. We can all recognize a bloodstain. If it's fresh, it's red. Older bloodstains are a reddish brown. But not all stains having the color of blood are blood. A number of liquids such as paint, rusty water, food coloring, salsa, and catsup can give the appearance of blood.
Upon finding a suspicious-looking stain at a crime scene, a forensic scientist will need to make a determination as to whether or not it is really blood. This is done by performing a presumptive test, so called because, if the test is positive, the investigator can presume the stain is actually blood.
Most presumptive tests for blood show a positive result by changing color when exposed to hemoglobin, the iron-containing protein in red blood cells responsible for carrying oxygen from the lungs to the rest of the body. Unfortunately, some plants, such as horseradish and potatoes, contain enzymes that can also induce a color change during a presumptive test for blood.
If these should be present at a crime scene, they could lead to a false-positive result. Nevertheless, these occasions are rare and the presumptive tests used by forensic scientists are reliable enough to have value. They almost all rely on a chemical process called oxidation—reduction.
Blood typing has been used for many years in forensic science and was the main source of blood determinations prior to deoxyribonucleic acid DNA being introduced as a more conclusive form of evidence 4.
Four main blood types are used for identification purposes, but there are eight groups, which are more specific and relate directly to the antigen present in the blood. In addition, the basic A-antigen and B-antigen in an individual's blood will also contain the presence of an Rh factor of positive or negative.
Once human blood is identified at a crime scene, the specific blood type can be determined. Unfortunately, this is not individualized to a specific person but helps narrow the percentage of the population that has that specific blood type. If blood typing is the only option in a case, the investigator could narrow the suspect pool by determining the blood type found at the crime scene and comparing the information to the blood type of each possible suspect. The most characteristic feature of blood is hemoglobin, and forensic tests for blood are based on detecting hemoglobin or its components 5.
Hemoglobin is the protein that transports oxygen between the lungs and all the tissues and cells of the body. Hemoglobin consists of two parts, -heme? The preliminary forensic blood identification tests are really tests for heme. They use certain dye substances that, when mixed with peroxide, will change color in a chemical reaction called -oxidation.?
There are protein enzymes in nature that will speed up this reaction, but heme will also speed up the reaction. Remember that enzymes are catalysts; they speed up reactions that are otherwise slow. Policies Schedule Changes This schedule is subject to change without notice. Registration and Fees Full payment must accompany all registrations. Course Confirmations A minimum number of registrations must be received for an in-person class to run as scheduled.
Transportation and Lodging Most locations are served by several major airlines. E-mail to a Friend. Return to Course Catalog. For example, unfixed livor blanches white when moderate pressure is applied, as opposed to fixed livor mortis, which remains the same color when pressure is applied. If livor mortis is noted on the deceased in areas not consistent with forming in the lowest parts of the body then the death-scene investigator should consider the possibility that the deceased was moved after death Horswell, b.
Victims may be found in contorted or apparently uncomfortable positions on the floor, commonly the bedroom or bathroom. Generally, the more contorted the body, the more sudden the death. Bodies found in awkward positions that compromise breathing can die of positional asphyxia. The chest wall must be able to rise and fall for respiration to occur.
If one is wedged too tightly in a position, the chest wall cannot rise and fall Wagner, Fig. Many inexperienced investigators focus on a major injury and neglect to evaluate the rest of the individual. This can lead to important oversights such as fingernail marks, bruises, and.
Seventy two-year-old man had lost the key of the door of his house in his vineyard and he tried to go in from a small hole which he made on the roof. He was stuck and found dead in the hole due to positional asphyxia.
Documentation of this inspection should be made noting the presence and absence of unusual markings or abnormalities. Descriptions of the state of rigor and livor mortis as well as the body temperature of a subject helps a forensic medicine expert to estimate the time interval since death. Environmental assessment, including temperature, heating or cooling systems, moisture, and wind conditions must be made at a death scene so that the environmental influence on a decedent can be determined.
The assessment should also include the types of clothing and jewelry. This information may be needed to assist in determinating the time a subject was last seen alive. Clothing should be appropriate for the weather and location found.
If not, it needs to be explained. One should also determine if the clothing fits an individual. If a subject is decomposing, then clothing may appear too small due to body swelling. If the clothing is the incorrect size, one must determine why. Was the person wearing someone else's when death occurred? Or, was the decedent redressed by another person after death? Note the cleanliness of the clothing. A variance in the clothing or body cleanliness may indicate that he was handled by another individual after death Dix et al.
General uncleanliness such as lack of bathing, very dirty clothes, urine -or feces- stained clothes, long and dirty nails, and poor oral hygiene may be due to alcoholism, drug abuse, or a mental disorder Wagner, Is the clothing worn properly?
Are buttons fastened and zippers closed? It is common to find opened zippers in intoxicated males or some elderly persons living alone. If the clothing is inconsistent with normal dressing techniques, consider whether a subject had a disability contributing to this behavior.
Jewelry should be carefully noted and reported as to its type, style, color and body location. All jewelry must be listed, regardless of its apparent value.
Obvious "missing" jewelry should also be noted, such as only one pierced earring, or no wedding ring on a married individual. Currency and credit cards should be handled as valuable items.
Currency should be counted in the presence of another and credit card details noted. If an investigator decides that these items may be given to the next-of-kin at the death scene, he must be certain that the relative has the legal right to such items. No analyses should be performed on a decedent's body at a scene, such as gunshot residue or fingerprinting, without the expressed consent of the forensic medicine expert responsible for the postmortem examination.
Clothing should not be removed, a body should not be cleansed, and liquids or powders should not be placed on the deceased as these might interfere with radiographs or chemical testing. If more than one hour has elapsed since the initial body assessment and the decedent is still at the scene, a second assessment should be recorded.
Generally, there is no correlation between facial expressions, body positions, and suffering. Pain and suffering can be assessed before and during the dying process, but it is done carefully and generally by the forensic medicine expert after evaluating the autopsy and investigative information.
This information can be useful to the family, and can become arguable in civil court cases Wagner, An investigator must also gather information that relates to cause and manner of death. Each type of death requires specific scene information. For instance, questions to be asked in a motor vehicle fatality would not be the same as those asked in an autoerotic asphyxia death.
Since different questions need to be asked, an investigational guide for each specific type of death can be very useful. For example, it is critical in suicides resulting from a handgun that investigators determine the handedness of a subject Dix et al.
The scene should be searched for a medical history in nearly all death investigations. This search may be as simple as finding an inhaler for asthma nearby a gunshot wound victim or as complicated as going through cabinets full of medication at a residence. Many people do not take the treatments the doctor ordered and reject advice given at the hospital. Only interviewing witnesses and searching the scene will reveal this information Wagner, Prior to a forensic medicine expert's arrival, law enforcement officers, paramedics, and other support personnel probably have communicated with individuals or witnesses at the scene.
A forensic medicine expert needs to know this initial information so that he can compare it with the decedent's body data and determine if there are any discrepancies. It is better to ask the question twice and get the same answer, than to accept as fact information that has been checked by one source. A forensic medicine expert needs to determine, for instance, if the body data rigor, livor, temperature, clothing, injuries, etc. Forensic medicine experts and law enforcement agents work cooperatively in a team effort.
Although the medical expert has jurisdiction over the body, law enforcement has jurisdiction over the entire scene. The forensic medicine expert is invited to the scene and, as a guest, must comply with house rules. In Britain, for example, several teams converge on a scene of crime, including photographers and video operators, and Scene of Crime Officers SOCOs whose function is to collect trace evidence. Scientists from the nearest forensic laboratory often attend with their police liaison officers, as well as fingerprint officers and, of course, the investigating officers from the Criminal Investigation Department.
The lead detective will walk the forensic medicine expert through the scene, relaying information and pointing out salient features. Where no such backup is available, the forensic medicine expert must try to collect trace evidence himself, but he should remain within the limits of his own expertise. The forensic medicine expert should accept the instructions of police officers in relation to the approach to the body so as to preserve the immediate environment as much as possible.
Out-of-doors access is often limited to a single pathway marked by tapes, and in a building a track to the corpse is usually pointed out by the detective in charge. The doctor should not touch anything unnecessarily and certainly not smoke or leave any object or debris of his or her own. The Locard Exchange Principle states that whenever two objects come into contact, a mutual exchange of matter will take place between them.
Linking suspects to victims is the most important and common type of linkage accomplished by physical evidence in criminal investigations. Linking victims and suspects to objects and scenes can also be accomplished by use of the physical evidence Miller, Fig.
The year-old murderer killed his employer in his workplace as he did not pay his salary. On the death scene investigation, a horror mask on the top and footprints of sports shoes of the murderer on the bottom were found. These evidences were used to determine the murderer. After surveying the overall death scene, it should be easy to recognize the sequence in which evidence is to be collected and areas to be searched and in what order.
The collection and search should be systematic, ensuring absolutely nothing is overlooked. In establishing the manner and sequence of collecting potential evidence by death scene investigators, consideration must be given to the possible destruction of evidence and which approach will yield the best result in terms of useful information Horswell, b.
Clues about the cause and manner of a death and who committed a crime may be found at a scene. The following list includes different types of evidence and how they are usually collected and preserved. Blood - Dried particles should be scraped into a drycontainer. Some dried areas may be sampled with a wet swab. A specimen should be dried before sealing it in a container. Articles of clothing or other objects containing blood may be submitted to a laboratory for sample removal by a technician.
Semen - An article of clothing containing semen should be collected or the specimen on the clothing can be lifted with water or saline. Fingerprints - Soft objects that leave an impression may be collected in their entirety. Prints on hard objects like glass or furniture should be lifted at the scene. Firearms and other weapons - These should be submitted to a lab without special treatment at a scene.
A technician must ensure proper handling so that fingerprints are not smudged or ruined. Bullets and cartridges - These should not be grasped with metal forceps because points of comparison may be damaged.
Hairs and fibers - These should be placed in separate containers and should not be crushed with hard objects such as metal tweezers. Suspicious foods and pills - Each item should be placed in separate containers or bags to prevent contamination.
Footprints and tire marks - At the scene, casts should be made and close-up photographs should be taken. Tool marks - There should be close-up photographs of the marks made by tools and, if possible, the damaged material should be removed for analysis by a lab technician.
Blood spatters - These should be photographed and described for analysis as to distance and angle of spatter. Samples may be removed for testing and preservation.
Other - Glass, soil, documents, cigarette butts, tobacco, and all items thought to be involved in arson should be collected and submitted to a lab.
Each item submitted to a lab should be referenced by either a photograph or written description as to its location in the scene. All containers with items submitted to the lab must be labeled on the lid and side of the container, with a case number, date, time, type of specimen, and name of the person who collected the specimen.
A "chain of custody" begins at this point and continues until a disposition of the specimen is completed Dix et al. Methods of searching critical areas include grids that are larger in less critical areas and smaller in critical areas, or searching in a clockwise or counterclockwise direction from a fixed point, or conducting a line strip search. All these form part of conducting a professional systematic search of a death scene.
A systematic approach to the searching of death scenes reduces stress and fatigue and ensures a more comprehensive search and recovery operation, minimizing the chance of losing potentially valuable evidentiary material Horswell, b. Any weapon or other item possibly related to the death and found at a scene should be brought to the morgue for analysis by a forensic medicine expert. Often, substances are the causative agent in the death.
All medication and alcoholic beverage containers should be confiscated as these will be invaluable to the toxicologists. Note the location where each item was found. Studies have shown that a fatal intoxicant is likely to be found in the same location as a decedent.
Any drug paraphernalia, notes, or any unusual item that might have been used by the subject should be confiscated Dix et al.
Interviews should include basic information such as the subject's identification, clothing, time, date, state of health, date and time the body was discovered, and medical, employment, and social history. Any recent events that may have a bearing on the death are also important.
A death investigator should always ask if a decedent had recently been involved in any potential harmful situations. This information may be extremely helpful if later attempts are made to make a prior incident a contributing factor in the death. If suicide is suspected, it is preferable to interview family members and close friends as soon as possible after the death is discovered.
This may preclude guilt-related, subconscious, erroneous statements made by loved ones several days later Dix et al. The general warmth or coolness of the hands and face can be assessed by touch, and the degree of rigor mortis felt by gently testing the limbs. The ambient environmental temperature must be taken as soon as possible after the discovery of the body, preferably by police scene of crime officers who usually arrive at the locus before the forensic medicine expert.
The ambient temperature should be taken as near to the body as possible, as microenvironments can exist, even inside buildings or rooms. Information should be sought as to how much disturbance of the ambient temperature might have occurred, such as opening doors and windows, or turning fires or central heating on or off, so that some idea of post-discovery distortions of temperature can be estimated later.
The insertion of a thermometer into the rectum at this stage in the investigation, as advocated by some textbooks, is controversial. At a scene of death, this usually means either pulling down trousers or pants, and otherwise disturbing clothing, often in cramped and ill-lit places, frequently out in the open. It also risks contaminating the rectum and perineum, by introducing seminal fluid from the anal margin into the rectum, making subsequent examination of that area and taking swabs for semen of reduced value.
As so many violent crimes now have sexual or homosexual overtones, the practice of taking rectal temperatures at the scene should be performed only if the forensic scientists or police scene of crime officers are satisfied that trace evidence from the clothing, swabs from the vulva, vagina and anus, etc. In other words, a cost-benefit analysis must be made at the scene, to decide if the difficulties of taking a rectal temperature are worth the small potential advantage of an earlier measurement.
In many cases, where the body has obviously been there long enough for the core temperature to have reached ambient - or where other circumstantial evidence has indicated that the time of death is known to a greater degree of accuracy that can be hoped for by thermometry - then nothing is lost by postponing the procedure until the body arrives at the mortuary for autopsy, which, in British practice, is usually directly after the body is moved from the scene.
If the autopsy is to be delayed for many hours owing to difficulties with transport or lack of facilities, then much more must be done at the scene and temperature measurements are justified.
An alternative is to use a place other than the rectum. The axilla and mouth give low readings, which cannot reliably be correlated with the deep temperature because of variable exposure to the air temperature. More useful is the auditory meatus or nostril, the thermometer or thermocouple probe being inserted as deeply as possible.
Using scene markers to determine when an individual died, though unscientific, is often more accurate than determinations made by scientific means. This is especially true in badly decomposed bodies. Scene markers include:. When the neighbors last saw the individual or observed a change in his habits. Different clues from a scene also must not be overlooked: Was food being prepared?
Was a major appliance on? Were there indicators as to a decedent's activities just prior to or at the time of death? A forensic medicine expert may use the answers to such questions to arrive at an estimation of the time of death Dix et al.
When the forensic medicine expert has made the best examination possible in the circumstances, his next function is to ensure that the corpse is removed to the mortuary for autopsy with the least disturbance and loss of evidence.
He should supervise the removal himself or at least delegate the duty to another person whom he knows is careful and competent. Each hand should be enclosed in a bag, secured at the wrist by adhesive tape or string. A similar bag should be placed over the head. The packaging medium may vary, but generally paper bags are recommended. The body should be placed gently in a 'body-bag', which has a zip closure, or moved on to a large, new plastic sheet, at least 2 metres square.
If a sheet is used, the edges should be wrapped over the body and secured with adhesive tape. The object of the exercise is to retain any loose objects, hairs and fibres that may be adhering to the body or the clothing. The sheet or bag is taken by the forensic laboratory after the body is removed in the mortuary so that they may screen it for trace evidence. The transport of the body is the responsibility of the police or other agency such as the coroner or his officer.
The body in its plastic wrapping should be placed in a rigid fibreglass 'shell' or ordinary coffin, and taken by hearse, van or police transport to the chosen mortuary. Physical damage during the removal should be avoided as much as possible, though in difficult or inaccessible sites this is easier said than done.
In fires, the body may be seriously damaged before or during recovery, sometimes because its presence is not suspected in the smoke-filled, often waterlogged, debris of a conflagration. Handling brittle, charred, bodies can easily cause the splits at joints that may mimic ante-mortem injuries. In summary, the function of a forensic medicine expert at any scene of suspicious death is to observe the situation, to conserve any fragile evidence, to supervise the removal of the body and offer an opinion, based on experience, about the nature of death where this can reasonably be done.
He is not there to act as a latter-day Sherlock Holmes, voicing unsubstantiated theories on non-medical matters, nor attempting to overinterpret the situation from the flimsiest of facts.
In the community, the most serious crime is that of the intentional killing of one person by another and it is therefore necessary that each of these events be thoroughly investigated by a team of specialists Horswell, b. Death scenes may be indoors or outdoors. The murderer may have intentionally altered the scene in an effort to mislead investigators or make a statement, usually a defiant one.
A crime scene altered in this manner is said to have been staged. What is the position of the body? What clothes are on the body and are they intact, dirty, torn, or rearranged?
If there is blood, is it spattered or pooled? Detailed photographs of the body and the surroundings are critical. Random murders usually are extremely rare. Possible motives for homicides include sex, financial need, crimes of passion, blackmail and self-defense, and there occasionally is no motive at all.
Establishing the cause of death is extremely important in any homicide investigation, because it usually provides the investigators with valuable evidence.
The cause of death in a homicide might be something such as asphyxiation, stabbing, gunshot wounds or poison. It is up to the criminal investigation team to ascertain whether the crime was accidental, a momentary loss of control on the part of the accused or a premeditated act, or perhaps it actually was suicide. The angle of entry of a bullet or knife gives investigators a clear picture regarding the intent of the accused.
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