GAITHERSBURG, Md. (WUSA9) -- A Maryland woman who helped put some of the worst criminals in the D.C. metro area behind bars is retiring after forty years as a fingerprint expert.
Like in the movie, Hidden Figures, Mary Ann Horton's important work was done behind the scenes. But our community is safer because of her.
"I got called in on Halloween to come and look at a latent print that they had discovered on a pillow case," began Mary Ann Horton, a fingerprint expert who helped put murderer Haden Clark behind bars in 1993.
"It's very unusual to be able to have a fingerprint on fabric because of the weave, it breaks the print up, makes it difficult to look at. But in this particular case, it was a very fine weave and the print was left in blood," Horton explained.
At his trial in Montgomery County, Clark pleaded guilty to stabbing 23-year-old Laura Houghteling to death in 1992. In prison, he confessed to murdering six-year-old Michelle Doer in 1986. Clark led police to the remains of both of those victims and he has claimed to have killed a dozen women from Maryland to Massachusetts.
Haden Clark, 65, is serving 60 years in prison.
Mary Ann Horton also matched a bloody footprint to the killer of Germantown's Monsignor Thomas Wells. It belonged to a homeless tree trimmer named Robert Paul Lucas, 26. He was convicted of second-degree murder in 2001.
"It's about finding the truth. About making sure that the right person comes to justice, but also that innocent people are not accused of something they didn't do," said Horton.
Mary Ann Horton has been scrutinizing fingerprints for forty years in Maryland. She started right out of high school because her parents couldn't afford college.
"So the FBI came to my high school and recruited. And the recruitment was a five-word spelling test. And I often joke that I got into this because I knew how to spell 'grammar.' Grammar was one of the words," she chuckled.
Horton has worked the past 37 years with Montgomery and Prince Georges County police in a combined unit. Matching fingerprints used to be a labor intensive ordeal. Automation made the process much easier, but computers can't do everything.
"The computer is good with coming up with things that are similar, but you still need a person to be able to make that final determination," she said. And a computer can not testify in court. Horton has testified more than a hundred times in criminal court cases.
While she has made thousands of matches over the year, the one that makes her the happiest is the match she found 35 years ago: She married her instructor Larry Horton.
Co-workers will throw a good-bye party next week for their own "Hidden Figure" and she'll go on her way to make her next mark.
