Trace Evidence

Tiny fragments of physical evidence such as hairs, fibers from clothing or carpeting, or pieces of glass are examples of trace evidence, and can be transferred when two objects touch or when small particles are disbursed by an action or movement. This evidence can be used to reconstruct an event or indicate that a person or thing was present. Careful collection of materials from a crime scene can yield a wealth of information about where a sample came from and how it helps to tell the story. This guide explains the principles of trace evidence, how and when trace evidence is used, common terms and other resources about trace evidence.

With funding from the NIJ, Dr. Michael Sigman and Mary Williams from University of Central Florida developed a method for analyzing fire debris samples that are highly contaminated with pyrolysis interferences. This technique provides an alternative objective method for classifying ignitable liquid residues, which is one of the only viable options for helping to progress fire debris analysis beyond a subjective comparison technique

The Organization of Scientific Area Committees for Forensic Evidence (OSAC) develops documentary standards for forensics through a standards developing organization or other consensus-based process that allows for participation and comment from relevant stakeholders. Standards under consideration as well as approved standards are available in the OSAC Registry. Standards are being developed for each forensic discipline.

As part of our mission to help North Carolina’s public defense community understand forensic science evidence and achieve better outcomes for clients, the office of the Forensic Resource Counsel continues our efforts to make information related to forensic science evidence more easily accessible to attorneys through this website. In that vein, we are pleased to …

The Justice Department and FBI have formally acknowledged that nearly every examiner in an elite FBI forensic unit gave flawed testimony in almost all trials in which they offered hair comparison evidence against criminal defendants over more than a two-decade period before 2000. Of 28 examiners with the FBI Laboratory’s microscopic hair comparison unit, 26 overstated forensic matches in ways that favored prosecutors in more than 95 percent of the 268 trials reviewed at the time of publication of this article.

A chemist at NIST has developed a portable version of his method for recovering trace chemicals such as environmental pollutants and forensic evidence including secret graves and arson fire debris. The briefcase-sized kit could enable detectives, field inspectors and others to carry with them a convenient version of NIST’s “headspace analysis” technique, which identifies solid or liquid compounds based on the makeup of vapors released into nearby air.  

For years, investigators have relied on the Paint Data Query database to identify the make of a vehicle by matching the physical attributes, chemical composition, and infrared spectrum of the paint, primers, and clear coating layers. However, there are concerns with the database, generic coding being one of them.

Two scientists with a long record of research into the forensic value of very small particle populations examined cell phones, handguns, drug packaging, and ski masks from the San Diego County Sheriff’s Office examine whether such particles are valuable as physical evidence.

Two related NIJ-supported studies evaluated the possibility of using an individual’s skin microbiome — a community of microorganisms that inhabit a specific environment — as a form of trace evidence from evidence found at a crime scene. The first study, led by Dr. Rob Knight of the University of California, San Diego, examined whether the sequence in which surfaces are touched by an individual, along with the number of times the surfaces are touched, influences the detection of the person’s microbiome.

The Journal of Forensic Sciences is now offering an early viewing of a new article by Microtrace scientists. This article is co-authored by Katie White and Christopher Palenik. This article explores the potential usefulness of subvisible toner cartridge particles as evidence in forensic investigations. Modern printing toners represent a prime example of subvisible particles that can be easily transferred to hands, clothing, and other surfaces.

A tissue containing a faint stain was submitted to determine if evidence of a make-up stain was present.  Although the tissue had been previously analyzed by another laboratory (to no avail) and only a single, barely stained area of the tissue remained, Microtrace, LLC was able to use light and electron microscopy to characterize the particles present.

Forensic Science International published a research article by Michael Cook in Nov. 2016. The study found that 85 percent of officers had 3-component GSR particles on their hands immediately following the start-of-shift handling of their firearms.

by Dennis L. McGuire, M.S., Forensic Magazine – discusses the lack of a uniform standard for GSR analyses based upon validated studies. States that until those studies are completed, “positive determinations of GSR should be seriously scrutinized.”

Article that summarizes the findings of a group of scientists and practitioners who met to address issues with gunshot residue analysis and attempt to create guidelines for this type of analysis. This document references several studies that have been published regarding contamination of subjects and proper collection, testing, and reporting procedures.

Offered by NIST

Offered By: The National Institute of Standards and Technology. Multiple Speakers. Achieved Videos Available.

Speakers: Dr. Tatiana Trejos, Dr. Luis Arroyo, and Dr. Suzanne Bell. Offered By: FTCOE. Achieved Video Available.

Speakers: David Moody, Barry Lavine, and David Stoney. Offered By: FTCOE. Achieved Videos Avaialble.

Speakers: Dr. Tatiana Trejos, Dr. Luis Arroyo, and Dr. Suzanne Bell. Offered By: FTCOE Achieved Video Available.

Speaker: Susan Gross, MSFS. Offered By: FTCOE. Achieved Video Available.

In this podcast episode, Josh Dubin speaks with Vanessa Antoun, Senior Resource Counsel at the National Association of Criminal Defense Lawyers (NACDL) to learn about Hair Microscopy Evidence.

Even when examined under a microscope, the similarities that can be observed between two hairs are open to wide interpretation, there are no definitive traits that can prove with any scientific certainty that a suspect’s hair matches a hair found at a crime scene. Yet hair comparison analysis was still being used to falsely identify and convict innocent people up until the year 2000 and people are still incarcerated who were convicted based on this false evidence.

So how did this evidence get admitted into courts in the first place? Learn more by listening to the podcast.

The goal of this focus area is to improve the field of glass evidence analysis by developing new matrix-matched glass standards and by evaluating more objective approaches to evidence interpretation, such as the likelihood ratio. The latter will be accomplished through the development of glass databases that may be used to assign a significance to an association or exclusion in forensic casework.

Databases which include reference collections of trace evidence for fibers, glass, automobile identification, paint, tape, plastic bags, powders and impressions.

Microtrace is a private microanalytical laboratory offering analytical services that are utilized by prosecutors, defense attorneys, police, forensic laboratories and, occasionally, the news media. Expert testimony and case reviews are provided. The website contains information about research and development in the field.

Nanoparticles and other subvisible particles potentially present in nearly all trace evidence are often overlooked in forensic investigations. NIJ-supported researchers have characterized several types of particles and developed detection methods.

The Organization of Scientific Area Committees Materials (Trace) Subcommittee for Forensic Science focuses standards and guidelines related to the examination and interpretation of physical evidence that may result from the transfer of small or minute quantities of materials (e.g., hairs, fibers, paint, tape, glass).

Relevant Chapters Include:

Experiment 8: Crime Scene Investigation: Safeguarding, Searching, Recognition, Documentation, Collection, Packaging, and Preservation of Physical Evidence

Experiment 9: Trace Evidence Collection and Sorting

Experiment 11: Examination of Human Hair 

Experiment 14: Examination of Trace Quantities of Synthetic Fibers

Santae A. Tribble was convicted of killing a taxi driver in 1978. He spent 28 years in prison for a murder that he did not commit. Key evidence at his trial came from separate FBI experts who testified that their scientific analysis proved with near certainty that Tribble’s hair was at the crime scene. However, subsequent DNA testing on the hair and on other evidence excluded Tribble as the source. Mr. Tribble was exonerated in 2012 and formally declared innocent.

In North Carolina, Timothy Scott Bridges was serving life for the rape of an 83-year old woman in Charlotte, in May of 1990. The evidence used at trial was microscopy hair evidence. He was convicted by a jury in Mecklenburg County for the charges of first-degree rape, assault with a deadly weapon with intent to kill on a handicap person, and felony breaking and entering and was granted a new trial in 2015.

Filed by the Innocent Network in support of the defendant.