Preservation of Physical Evidence
in Sex-Related Death Investigations
By Vernon J. Geberth, M.S., M.P.S.
Author of Practical Homicide Investigation, Copyright 2003
Reprint: Law and Order, Vol. 51, No. 7, July, 2003
Article Expanded for Research Material
Return to Research Materials
The recovery and collection of evidence in sex-related homicide and death investigations is of paramount importance to the overall investigation. Although the general principles of collection, chain of custody and preservation remain the same, there are unique aspects to the types of evidence encountered in sex-related events. Sex-related homicides frequently result in various kinds of personal evidence including body fluids, such as semen, sperm, blood and saliva, as well as hairs and fibers and other microscopic evidence, which may be lost or contaminated due to any number of variables ranging from the dynamics of the event and the environment of the scene to the actions of police personnel at the scene. This article will focus on definitions and classifications of evidence, enhancement procedures to visualize certain types of evidence, and the practical application of the collection, chain of custody and preservation of evidence in sex-related homicide and death investigations. The article will conclude with a Sex-Related Crime Scene CHECKLIST excerpted from the author's book, Practical Homicide Investigation.
General Types of Evidence
- Physical Evidence
- Testimonial Evidence
- Documentary Evidence
- Behavioral Evidence
In Practical Homicide Investigation each of these general types of evidence become crucial in the identification, apprehension and subsequent prosecution of offenders. However, the investigator should appreciate the nature of physical evidence.
Physical evidence is any tangible article, small or large, which tends to prove or disprove a point in question. It may be used to:
1. Reconstruct the crime
2. Identify the participants
3. Confirm or discredit an alibi
The proper collection and disposition of physical or trace evidence from the crime scene and the body of the deceased is of the utmost importance to the investigation ad eventual court presentation. The evidence must have been obtained legally in order for it to be admissible. Therefore, it is imperative that both the legal authority to collect the evidence and the proper collection techniques be considered prior to the actual collection of the evidence. (See Law and ORDER Article entitled; PRACTICAL CRIME SCENE INVESTIGATION: Legal Considerations)
Classifications of Physical Evidence
Class evidence is that which cannot be forensically identified with a specific source to the exclusion of all others. Examples are the non-DNA analysis of:
Individualistic evidence is evidence that can be positively and forensically identified with a specific source to the exclusion of all other sources. Examples are the DNA analysis of:
|BODY FLUIDS and HAIR|
TYPES OF PHYSICAL EVIDENCE
Is temporary in nature. Examples: Odors, Temperature, Imprints and indentations in soft or changing materials. (butter, wet sand, snow or mud.) Markings i.e. lividity, blood spatters on moveable objects.
Is produced by contact. Blood splatter, glass fracture patterns, fire burn patterns, Furniture position patterns, projectile trajectory, tire marks, M.O., clothing or article patterns, powder residue patterns.
Caused by an action or event. Lighting conditions at scene. Odor, color, direction of smoke. Flame (color, direction, temperature) Location of evidence in relation to the body. Vehicle (locked or unlocked; lights on or off, window open or closed, radio on or off, mileage)
Generally produced by physical contact of persons, objects, or between persons or objects. THE LINKAGE CONCEPT.
TRACE AND TRANSFER EVIDENCE
Practically speaking, there are two types of transfer evidence; trace transfer and pattern transfer evidence. Examples of' commonly encountered trace transfer evidence include hair, fibers, blood, semen, glass, and soil. Examples of pattern transfer evidence are imprint and impression evidence. Many times transfer evidence is a combination of trace and pattern components such as bloody shoeprints, hair and fibers, greasy fingerprints, or fabric impressions.
There is a principle in homicide investigation that refers to a theoretical exchange between two objects that have been in contact with one another. This theory of transfer or exchange is based on Locard's "Exchange Principle." Edmond Locard, a Frenchman, who founded the University of Lyons' Institute of Criminalistics, believed that whenever two human beings came into contact, something from one was exchanged to the other, and vice-versa. This exchange might involve, hairs, fibers, dirt, dust, blood and other bodily fluids, as well as skin cells, metallic residue and other microscopic materials. In Practical Homicide Investigation Locards' principle is summed up as follows:
1. The perpetrator will take away traces of the victim and the scene.
2. The victim will retain traces of the perpetrator and may leave traces of himself on the perpetrator.
3. The perpetrator will leave behind traces of himself at the scene.
The goal is to establish a link between the various facets of the crime scene, the victim, physical evidence, and the suspect. All of these components must be connected for the successful resolution of the case. The LINKAGE CONCEPT rests on the principle of the "Theory of Transfer and Exchange." Remember: Anything and Everything may eventually become evidence.
A direct transfer occurs when materials are transferred from the original source to another person or object. An example would be a bleeding victim's blood found on the suspect or his clothing. Or, a latent fingerprint of the suspect discovered in the crime scene and/or the suspect's semen recovered from the victim.
An indirect transfer occurs when trace evidence, which was directly transferred to one location is then transferred again to another location. An example would be rug fibers at the crime scene, which had been transferred to the clothing of a victim, are then found in the suspect's car after he transported the body to the dumpsite.
Procedures for Collection of Evidence
In order to be introduced as physical evidence in a trial, an article must: Be properly identified Show a proper "Chain of Custody" Be material and relevant Meet all legal requirements:
- Be properly identified
- Show a proper "Chain of Custody"
- Be material and relevant
- Meet all legal requirements
The crime scene technician or crime scene investigator who is summoned to the scene should have operational supervision over gathering, collection, and marking of evidence for identification. However, the investigator assigned to the case is still in charge of the investigation and should be consulted prior to any evidence gathering or crime scene processing.
The proper collection and disposition of evidence will be accomplished if the following guidelines are adhered to:
- Each piece of evidence should be marked (on the container or item as applicable) to show its original position and location. This information should also be recorded in the investigator's notebook.
- Each article should be marked distinctively by the searching officer to identify the person who found the particular piece of evidence. In cases of small or fluid specimens this marking is done on the container.
- Each item should be described exactly and completely with the corresponding case numbers affixed and the date and time of collection indicated.
- Each item should be packaged in a separate, clean, and proper sized container to prevent cross?contamination or damage.
- Each package should be sealed to retain evidence and prevent any unauthorized handling.
- Each piece of evidence should show proper disposition:
a. Police department laboratory
b. Property clerk's office
c. FBI Laboratory
- Proper records should be kept regarding each piece of evidence showing chain of custody. These records should reflect any movement of the evidence from the point of origin to its final disposition.
Remember, each item should be photographed before it is collected as evidence. These photographs should include a long-range view to show the relationship of the object to its surroundings and a close?range view to show the actual item being collected. (See Chapter 6 in Practical Homicide Investigation: Tactics, Procedures, and Forensic Techniques, 1996.
FIELD TEST REAGENTS
Tests for the Presence of Blood
This test is performed by rubbing a cotton swab that has been moistened in a saline solution on the suspected blood stain. A drop is added to the swab then a drop of hydrogen peroxide 3%. A positive reaction will turn swab PINK to RED within 15 seconds
LEUCOMALACHITE GREEN (LMG)
This test is performed the same way as above. A positive reaction is indicated by a GREENISH-BLUE color that will appear almost immediately.
This reagent is sprayed onto the object to be checked. However, it must be viewed in total darkness. In positive reaction will luminesce VIOLET within 5 seconds.
This test is performed by rubbing a cotton swab that has been moistened in a saline solution on the suspected blood stain. A drop is added to the swab then a drop of hydrogen peroxide 3%. A positive reaction is indicated by an intense BLUE color.
TETRA-METHYL BENZIDINE (TMB)
Another in a series of presumptive tests that is specific for BLOOD. TMB is an enhancement reagent. The TETRA-METHYL BENZIDINE reacts with the HEME in the blood. Spray the surface lightly 2 to 3 times about 10 inches away from the surface. The Bloody Imprint Pattern should turn a Greenish-Blue. Over spray may give a very Dark BLUE pattern and mask ridge patterns.
This is a protein reactant, which does not ordinarily react with household cleaners like Luminol does. Hemaglow also glows brighter and can be photographed with a flat plane camera.
(LCV) A new positive blood identifier that turns permanent VIOLET when in contact with blood. Leucocrystal violet can be testified to in court as a blood identifier at the scene without further testing to identify the stain as blood.
Tests for the presence of Body Fluids
|SEMEN||Acid Phosphatase tests|
|URINE||Creatinine, urea tests|
|GASTRIC CONTENTS||Gastric acid|
PATTERN ENHANCEMENT REAGENTS
Protein Enhancement Reagents
Ninhydrin detects trace amounts of amino acids associated with body secretions. The amino acids are transferred with the sweat from the pores of a finger, palm or the sole of the foot. Amino acids are easily absorbed into absorbent and partially absorbent surfaces such as paper, unfinished wood, cardboard, leather, etc.
COOMASSIE BRILLIANT BLUE (R250)
Coomassie Blue is a general protein that works well with bloodstains. Coomassie is a more sensitive, general protein stain, than crystal violet stains.
CRYSTAL (GENTIAN) VIOLET
Crystal violet works exceptionally well on adhesive surfaces such as tapes.
This is a protein reactant, which is sprayed onto the suspected area. NAPHTHOL, which is the AMIDO BLACK powder is mixed with Glacial Acetic Acid and Methanol. The formula is to mix 2 grams NAPHTHOL 100 ml Glacial Acetic Acid and 900 ml of Methanol.
THE PROCEDURE: Set the prints with Methanol then spray the area with AMIDO BLACK. Rinse with 100 ml Glacial Acetic Acid and 900 ml of Methanol. Rinse with water. Clean with Clorox.
Fatty Acid, Elements and compounds Enhancement Reagents
SMALL PARTICLE REAGENT
SUPERGLUE (Cyanoacrylate) FUMING
Method for Diagnosing Abrasions, Lacerations and Other Skin Disruptions in the Perineum and Perianal Areas.
According to Dr, Frederick T. Zugibe, Chief Medical Examiner, Rockland County, New York, an excellent procedure in determining sexual assault injuries can be visualized by the application of Toluidine Blue in .01% solution and/or Methylene Blue or Azure. Toluidine stains ground substance or mucopolysaccharides, which are found in abrasions as well as other skin injuries. The intact skin will not stain but injured skin will be visualized with the application of Toluidine Blue and/or Methylene Blue or Azure. This test is extremely effective in child sexual abuse cases. It can also be administered by doctors in Hospital Emergency Rooms, who treat live victims of sexual assault to document the presence of mucopolysaccharides. A simple color Polaroid taken before and after the application produces excellent documentation of sexual abuse, which can be used in trial. Toluidine Blue is applied with cotton or gauze to the area of suspected trauma. The excess is wiped-off with a K-Y jelly or similar substance. The stain will remain in the area of trauma.
SEX RELATED CRIME SCENE CHECKLIST
- Physical evidence in the form of seminal fluid must be collected as soon as possible before it is lost or destroyed. Samples can allowed to air dry naturally or you can use a hair dryer on low speed. Wet samples can be drawn into an eyedropper and should be placed in a sterile test tube. Dry stains will have a stiff "starchy" texture. If on clothing submit entire article, being careful not to break or contaminate the stained area. Consider DNA testing technique requirements.
- Blood (wet) should collected using an eyedropper and transferred to a sterile container. The blood can be put into a test tube with EDTA, an anti-coagulant and refrigerated. Small amounts can be collected using 100% cotton swab, #8 cotton thread, or gauze pad. Allow swab to air dry and place in sterile container. Consider DNA testing techniques.
- Blood stain, spittle and hair (including pubic combings) should be obtained at the scene; properly packaged and forward to lab. Consider DNA testing techniques.
- Trace evidence found on the victim and/or upon victim's clothing should be collected. Search for hair, fibers and other microscopic evidence. Use forceps, vacuum cleaner fitted with an in-line cannister attachment in the hose, or use tape. Tape and forceps is the best method so as to not contaminate samples.
- Bruises and marks on the victim, including the presence of sadistic injuries should be noted and documented in the investigative notes.
- Urine or feces may be left at the scene by the assailant. This evidence should be recorded and collected. Urine can be removed by eyedropper or gauze. Place in a sterile test tube or other container. If on clothing submit entire article. DNA Testing can be performed on urine.
- Fingernail scrapings should be obtained for an analysis of any blood, skin or hair from the perpetrator. Consider DNA testing technique.
- Confer with the Medical Examiner and assure that specimens are taken from the body. (e.g. hair from various areas of the body. A separate comb should be used for each area)
- In addition, vaginal washings, as well as anal, nasal, and oral swabs should be requested for serological evaluation and examination. Consider DNA testing technique.
- Examine the scene for evidence of a struggle. The presence of torn clothing, missing buttons, ripped textiles, marks on the ground or floor and blood splatters must all be photographed, documented, and collected as evidence.
- Homicides involving mutilation may yield clues such as style of attack, the type of weapon used, the amount and location of mutilation, the position of the body, etc. These items should be recorded.
- If a suspect has been taken into custody, his or her clothing should be taken and an examination conducted for any physical evidence. Examine for hairs and fibers.
- Each piece of evidence should be packaged in a separate container in order to prevent cross contamination.
- The suspect's body should be examined for any fingernail scratches, bite marks, or other indications of a violent struggle. Penile swabs for suspect offenders to collect blood, epithelial, cells and any other evidentiary materials.
- Hair and blood samples should be obtained (Assure that any such samples are obtained legally.)
- The body should be examined for the presence of bite mark evidence. Collect and record:
- Saliva washing of the bite mark area for blood grouping and or DNA. Use 100% cotton dampened in distilled water. Important: Obtain a control sample from another area of the body.
- Photograph the bite mark. Obtain B&W and Color photos. Use a rule of measure and obtain an anatomical landmark
- Casting (if possible) Use dental materials.
In sex-related homicide cases, basic evidence collection procedures acquire an increased importance. Human behavior patterns and psychosexual activities, not generally amenable to ordinary collection techniques become additional factors to consider in determining the reason and motive for the killing. Practical experience in homicide investigation coupled with an understanding of human behavior patterns and human sexuality are important prerequisites in analyzing these types of cases.
These copyrighted materials have been excerpted with permission of the author from Practical Homicide Investigation: Tactics, Procedures, and Forensic Techniques Third Edition 1996 CRC Press, LLC and Sex-Related Homicide and Death Investigations: Practical and Clinical Perspectives (In Press).
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