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Number two, YSTR DNA. Now, this type of testing zeros in on one thing and one thing only, the Y
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chromosome, which only exists in men. So, it can only trace DNA passed down from father to son. This type of testing
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can be particularly powerful when evidence has a mix of male and female DNA, like for example, what could be
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present in a sexual assault kit. By isolating the Y chromosome, labs can pull out just the male DNA from the
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sample. One chilling example of this? The 1991 yogurt shop murders in Austin, Texas. [music]
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At the time, YSTR testing was brand new, and the district attorney overseeing the
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case decided to give it a shot. Investigators believed that at least one of the victims in this case had been
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[music] sexually assaulted, and this test paid off. They pulled a partial male DNA profile from the evidence.
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>> [music] >> But, in the '90s, that profile didn't match anyone in the system, so the case
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went cold. Decades later, in 2025, everything changed when police received a report from a South Carolina state lab
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that linked the yogurt shop unknown YSTR profile to a known YSTR profile from a 1990 sexual assault and murder out of
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Greenville. The suspected killer? Robert Eugene Brashers, a known serial rapist and killer who had taken his own
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life back in 1999. From there, investigators were able to use other evidence to connect Brashers
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to the yogurt shop murders, bringing long-awaited answers to a case that haunted Texas and us crime junkies for
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more than 30 years.