The incident happened Wednesday afternoon. The woman told police she was attacked and robbed at knifepoint while she was on a walk.
The district attorney's office said the arrest was aided in part by data from a GPS bracelet obtained by Suffolk prosecutors in another case.
Ashton Davis, 23, was taken into custody and then held on $50,000 cash bail at his arraignment Friday. He covered his face during the court appearance.
Suffolk Country Assistant District Attorney Kristina Kerwin said, "He was wearing a GPS device which placed him at the exact place of the assault at the time it occurred."
Davis was wearing the GPS bracelet because is charged with rape in the other case. That incident is alleged to have occurred on Feb. 8 at night in Roxbury. The Jamaica Plain attack, however, allegedly happened in the middle of the day.
Prosecutors said the victim went to the Arboretum to study just after 11 a.m. That's when Davis allegedly pulled up on a bike, with a knife. He first robbed her, then sexually assaulted her, according to prosecutors.
A friend of Davis' said that he's bi-polar and has anger management issues. She told FOX that he lives with her family in a Roxbury apartment building. She also said Davis went for bike ride Wednesday morning, but isn't certain where he went..
"I don't know because he said he was gonna go for a walk or a bicycle ride," his friend said.
Tom Karp, Davis's Defense lawyer, is concerned about the evidence and says the victim wasn't certain Davis was the man who sexually assaulted her.
"According to the police report, she said maybe," Karp said.
But based on the pending rape charge from February and the GPS evidence, the judge disagreed. And now women who walk in the Arboretum, even during the day, say they'll be more vigilant.
"I do take more precautions when I am walking. I am very aware of my surroundings, how people approach me, what they look like," one walker said.
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