Hair evidence at a crime scene is collected with sterile forceps for visible strands, adhesive tape lifts for textured surfaces like clothing and upholstery, a fine-toothed comb for hairs on a body, or a filtered vacuum for large areas. Whichever method fits the surface, the goal is the same: lift each strand intact, keep it isolated from every other sample, and document exactly where it came from. How the collection is done, and how the hair is packaged afterward, decides whether it survives as evidence or gets challenged out of the case.
Forceps for Visible Strands
When a strand is visible on skin, a smooth surface, or a discrete object, an investigator picks it up with clean forceps and places it on a piece of clean paper, which is folded to secure the hair inside.1National Institute of Justice. Collecting DNA Evidence at Property Crime Scenes – Hair and Fiber This is the preferred approach because it gives the collector the most control: the root is not damaged, the exact location is recorded, and each strand stays isolated. It is the standard method for hairs found on a body during examination.
Tape Lifts for Clothing and Fabric
Textured surfaces like clothing, carpet, and upholstery hide individual hairs. Investigators press clear adhesive tape against the surface and peel it away, and any hairs clinging there transfer to the tape. The tape is then placed sticky-side-down onto a clean backing sheet for preservation and transport.1National Institute of Justice. Collecting DNA Evidence at Property Crime Scenes – Hair and Fiber Tape lifts sweep a large area quickly, but they pick up everything on the surface, so the lab has more sorting to do downstream.
Combing
To recover loose hairs from a person’s head or body, a clean fine-toothed comb is drawn through the hair over a sheet of clean paper. Whatever falls free lands on the paper, and the comb and paper are folded together and packaged as a single unit so nothing is lost. Combing is used primarily during the collection of known reference samples rather than off surfaces at the scene itself.
Vacuuming
For a full room or the interior of a vehicle, investigators can use a vacuum fitted with a filtered trap that captures whatever is drawn in. It is the least desirable method. If the equipment is not scrupulously cleaned between uses, hairs from a previous scene can contaminate the current one.1National Institute of Justice. Collecting DNA Evidence at Property Crime Scenes – Hair and Fiber Vacuuming also destroys any record of where on a surface a specific hair was found, which weakens the story that evidence can tell at trial.
Whatever the method, fresh gloves and sterile tools are used for each collection to prevent one sample from contaminating another.
Why the Root Matters During Collection
Collection technique is not arbitrary because different parts of a hair carry different kinds of DNA. A hair pulled out with the root attached can contain nuclear DNA, which produces a profile unique to one individual. Shed hairs almost never yield a usable nuclear DNA profile because the root cells have largely degraded.2National Center for Biotechnology Information (NCBI). Fragmented Nuclear DNA Is the Predominant Genetic Material in Human Hair Shafts A rootless shaft can still provide mitochondrial DNA, but mitochondrial DNA is inherited through the maternal line, so it points to a family group rather than one person. Everyone sharing the same maternal ancestry carries the same sequence.3National Center for Biotechnology Information (NCBI). Mitochondrial DNA in Forensic Use That is why forceps and careful handling matter: preserving the root is the difference between evidence that identifies a specific person and evidence that identifies a lineage.
Where Investigators Look
Hair transfers easily through contact, so anywhere a person may have touched, leaned against, or struggled on is worth checking. Clothing, bedding, upholstery, vehicle headrests, weapons, ligatures, and the bodies of victims or suspects are common locations. Drains, brushes, hats, and personal items at the scene are also searched.
One thing to keep in mind: a person can unknowingly carry someone else’s hair on their clothing and deposit it somewhere later. Indirect transfer happens routinely, and hairs picked up from one surface can persist long enough to end up somewhere their owner never went. A hair at a scene does not, on its own, prove its owner was ever there. Context and corroborating evidence do that work.
Packaging and Preservation
A strand that survives collection but degrades in storage is worthless at trial. Individual hairs or small groups go into a paper fold called a bindle: a sheet of clean paper folded to enclose the hair, then sealed with tape. The bindle is placed inside a labeled envelope. Paper is preferred over plastic because static in plastic bags can pull fine hairs against the walls where they cannot be cleanly recovered, and paper lets moisture escape, which matters for biological material.
Each item gets its own package. Hairs from a victim’s clothing go in a separate envelope from hairs found on a weapon, even if they look identical. Every envelope is labeled with the case number, the date and time of collection, the exact location where the hair was found, and the initials or badge number of the collector.1National Institute of Justice. Collecting DNA Evidence at Property Crime Scenes – Hair and Fiber
If a hair is wet from blood, water, or another fluid, it has to be air-dried before going into its final sealed package. Sealing wet biological evidence accelerates degradation and encourages mold, both of which destroy DNA.4National Institute of Justice. Air-Dry Evidence When drying is not possible at the scene, the evidence goes into a leak-proof container, then to a drying facility, then into paper for cold storage.
Chain of Custody
From the moment a hair is lifted off a surface until it appears in a courtroom, every person who handles it signs a log recording their name, the date and time, and the reason for the transfer. This is the chain of custody, and it is what proves the evidence was not tampered with, contaminated, or swapped.5National Center for Biotechnology Information (NCBI). StatPearls – Chain of Custody
An unbroken chain is a prerequisite for admissibility. A gap, a missing signature, or an unexplained stretch of time when no one can account for the evidence gives the defense grounds to challenge authenticity. Courts have excluded otherwise solid evidence over documentation failures.6National Institute of Justice. A Chain of Custody – The Typical Checklist For something as small as a single hair, the risk of a successful challenge is even higher, because it is harder to prove a strand was not accidentally introduced after collection.
What Collection Can and Cannot Prove
Careful collection is only worth what the underlying analysis can deliver, and hair comparison has a troubled record. A joint FBI and Department of Justice review released in 2015 found that in 268 cases where examiners had testified in ways favoring the prosecution, roughly 96 percent contained erroneous statements about microscopic hair comparison.7Federal Bureau of Investigation. FBI Testimony on Microscopic Hair Analysis Contained Errors in at Least 90 Percent of Cases in Ongoing Review A 2009 National Academy of Sciences report concluded that no scientifically accepted data exists on how often specific hair characteristics appear in the population, and there are no uniform standards for how many features must align before an examiner can call it a match.8National Institute of Justice. Strengthening Forensic Science in the United States – A Path Forward
A hair with an intact root can still produce a nuclear DNA profile that identifies one person to a near-certainty, and mitochondrial DNA from a rootless shaft can exclude a suspect or confirm a maternal lineage. Microscopic examination still helps labs decide which hairs are worth DNA testing. Collection and preservation have to be meticulous either way, because no analytical technique can rescue a contaminated or degraded sample.