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Mason Hall, -- who was 17 at the time -- attacked the 19-year-old victim, held a black semi-automatic handgun to her head, and forced her into a secluded pasture off of the walking path, where he sexually assaulted her the morning of August 1, 2017, according to the Montgomery County District Attorney's office.
At the time of the attack, the Hall was wearing a dark-colored hooded sweatshirt, despite the 86-degree heat, and attacked the woman from behind while she was on a stroll, so there was limited descriptive information that would allow police to identify him, authorities said.
However, DNA was recovered.
Parabon NanoLabs produced a composite illustration—like a high-tech police artist’s sketch— of what the suspect could look like, based on his DNA profile, which was found to be 52 percent European and 45 percent African, the DA's office said.
The $10,000 reward and illustration -- which bears a striking resemblance to Hall -- generated multiple tips but none led to the suspect.
Following the generation of the DNA profile, detectives then began looking at familial DNA, or partial matches to the suspect's DNA.
Eventually over the course of 22 months, with help from the FBI, investigators were able to identify the suspect as Hall.
Hall had been involved in an incident in September 2017, where Norristown police recovered a bloody hammer, the DA's office said.
On Sept. 27, 2019, Montgomery County Detectives retrieved the bloody hammer from police evidence and submitted it to the Philadelphia Police Office of Forensic Science, which determined the DNA matched the sexual assault suspect.
On Oct. 18, 2019, Hall was arrested at his home in Norristown, which is 1.4 miles from the site of the attack, the DA's office said.
“Since we had our attacker’s DNA, we always knew who he was, but it took 27 months of high-tech scientific efforts and thousands of hours of old-fashioned police work to track down this violent criminal and make this arrest,” DA Kevin Steele said in October 2019.
“Rapes and sexual assaults where a gunman attacks an unknown victim are, thankfully, rare in Montgomery County, and we used every avenue available to solve this violent crime.”
Hall also pled guilty Tuesday to firearms charges, terroristic threats, and related charges stemming from the gunpoint assault.
He will be sentenced in late September and will be facing a maximum of 22 to 44 years in prison.
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