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How hair helps solve crimes

July 11, 2019

Hair under a microscope File under “Things you only think about when watching CSI:” Hair can help solve crimes. It may sound far-fetched, but it turns out you can tell a lot about a person by examining their hair. Just ask the Bureau of Criminal Apprehension (BCA).

Law enforcement across the state can send lots of different evidence to the BCA for examination. And because humans shed about 100 hairs a day from their heads, hair sometimes ends up at crime scenes and, as such, is known as “trace evidence.”

When an investigator finds hair at a crime scene or on a crime victim, they can send the hair to a forensic scientist, who can analyze it. At the BCA’s Trace Evidence Laboratory, forensic scientists use powerful microscopes to look carefully at the hair. This microscopic hair examination can help scientists determine whether the hair is from a human or an animal. If human, it can tell scientists about racial origin and the body area it came from. In addition, they can tell whether the hair was forcibly removed, artificially treated, or came from a deceased person. If they have a known hair sample, they can view them side by side in a comparison microscope, looking for structural similarities that can show whether they came from the same human or animal.

As an example, an investigator may find a hair on a crime victim’s jeans. If the hair is consistent with that of the suspect, that may provide evidence of an association between the suspect and the victim.

But that’s not all the BCA can do with hairs found at crime scenes. The Trace Evidence Laboratory can also determine whether the hair is suitable for nuclear DNA analysis (“nuclear” here means that they analyze the nucleus of the cell). To be analyzed in that way, a hair has to have a root or tissue still attached. If it does, it gets sent to the BCA’s DNA Laboratory.

If there is no root or tissue attached, the DNA Laboratory can still do mitochondrial DNA testing (which is done by examining a cell’s mitochondria, which float inside a cell but outside the nucleus). Either way, it can help link a suspect to a crime.

Key evidence in several high-profile Minnesota cases has come from DNA testing on human hair. You may remember Cally Jo Larson, who was murdered in 1999. A human hair found in her home contained DNA matching that of Lorenzo Sanchez, who was eventually convicted of her murder. Or Sharon Bloom, whose murderer Stephan Zanter was convicted after DNA testing on a hair found on her body showed that the hair belonged to Zanter. And most recently, BCA scientists tested hair evidence in the effort that eventually led to the major break in the case of Jacob Wetterling, and the eventual conviction of Daniel Heinrich.

Hair may not seem very important in the face of major crimes like these, but with dedicated forensic scientists in state-of-the-art labs, it can mean the difference between an unsolved case and a convicted killer.