Category Archives: Trace & DNA

New Study on Survivability of DNA Evidence

A new study published by the NIJ, demonstrates positive recovery of DNA for up to 10 days following intercourse. Given various circumstances that may lead to delays in reporting or testing, it’s good to know that current testing methods may still yield results even with a substantial delay.

The study can be accessed here (in .pdf format):  https://www.ncjrs.gov/pdffiles1/nij/grants/248682.pdf

Trace Evidence: Hair

by Kathy Steck- Flynn

Edmond Locard was the founder of the Institute of Criminalistics at the University of Lyon in France. Locard believed that that when on person came in contact with another person or object a cross transfer of minute particles occurred. This theory became known as the “Locard Exchange Principle”. Locard believed that crimes could be solved by inspecting the “dust particles” carried to and from a scene. This science is known today as criminalistics and has led to the rise of the forensics laboratory (from Mount Royal College background notes FORE 4407 section 3: Unit 4) Francois Goron, head of the French Surete, seems to be one of the first modern investigators who tried to use hair to identify a killer. In his first case hairs found clutched in a dead woman’s hand could not be identified as human simply because there was no information on the subject.

The inability of the scientific community to distinguish between animal and human hair raised interest in the analysis of hair. In the years that followed researchers began to collect information about the structure of human and animal hair (Block, 1979). In 1899, several years after his original failure, in a case known as “L’affaire Gouffe” Francois Goron was able to establish that a murder victim’s hair had been dyed. Establishing this simple fact led to the identification of Gouffe’s body and subsequently to the arrest of his killers (Block 1979). Francios Goron had successfully used forensic hair examination to solve a crime. Continue reading

Interpretation, Collection and Preservation of Glass Fragments

By Kathy Steck-Flynn

A man is found dead in an abandoned house. Upon examination the medical examiner finds that the man was killed by a single gunshot to the head. Three local teens where observed near the house two days earlier. They are picked up and questioned by police. When pressured, the teens admit to having stolen one of the boys’ father’s guns. They had taken turns shooting at the windows of an abandoned house.

The teens admit that John shot the gun first, then Jay and last was Fred. At the scene the investigators find three bullet holes in a window. They analyze the angle of each bullet hole in relation to the victim and find that the bullet which passed through the far right side of the window pane is the one which fatally wounded the man. Continue reading

Condom Trace Evidence: A New Factor in Sexual Assault Investigations

By Robert D. Blackledge, M.S.
Mr. Blackledge is senior chemist at the Naval Criminal Investigative Service Regional Forensic Laboratory in San Diego, California.

This Article Originally Appeared in the FBI Law Enforcement Bulletin, May 1996.

(Offenders are changing the nature of sexual assault investigations by wearing condoms.)
In an age filled with potentially fatal sexually transmitted diseases, more and more individuals practice safe sex. Even perpetrators of sex crimes have begun to wear condoms.1 It is not likely that a fear of disease prompts this behavior. Rather, just as a burglar dons gloves to avoid leaving fingerprints, sexual offenders now wear condoms to avoid depositing seminal fluids. Continue reading

Serological Evidence in Sexual Assault Investigations

By Robert R.J. Grispino, M.A.
Special Agent Serology Unit, Laboratory Division FBI Headquarters

This Article Originally Appeared in the FBI Law Enforcement Bulletin, October 1990.

NOTE: The following article presents a purely scientific approach to sexual assault evidence collection. The scientific step-by-step procedures that are explained here should always be accompanied by supportive treatment of the victim. It should also be noted that the investigating officer will be responsible for both overseeing the execution of the medical procedures described and managing the collection of the physical evidence.

Police officers throughout the United States routinely handle and oversee sexual assault investigations. Yet, these officers rarely receive training on the proper methods to be used for sexual assault evidence collection and preservation. As a result, valuable physical evidence may either be overlooked or inadvertently allowed to deteriorate biologically. This article establishes proper evidence collection and preservation protocol in sexual assault matters and demonstrates how modern forensic serology can aid in the eventual successful prosecution of the assailant. Continue reading