We can now close the book on one of the two local cold cases either solved or advanced by a relatively new science-based investigative technique. After more than a decade, the victim of a brutal sexual assault in Acton finally received the justice she deserved. And in the other case, a suspect has been identified and charged in a “horrific” sexual assault that had “haunted” the Framingham community for more than 30 years.

That Acton cold case reached its conclusion last week when a Middlesex Superior Court judge sentenced Christopher Aldrich, 30, of Lunenburg, to 15 years in prison for raping a 22-year-old woman at knifepoint in June 2013. According to authorities, the woman was waiting alone at the South Acton Commuter Rail Station when a stranger approached her. The man brandished a knife, threatened her, and raped her at knifepoint.

He then fled the scene on foot. The victim called police and despite a thorough search, authorities were unable to locate the suspect. The victim was taken to a nearby hospital where a trained sexual assault nurse examiner treated her.

Forensic evidence collected during the examination was sent to the State Police Crime Laboratory, where chemists developed a detailed DNA profile of the attacker. However, comparisons with state and national offender databases yielded no matches. For more than eight years, the perpetrator remained unidentified.

The case finally gained traction in 2021, when prosecutors and police authorities enlisted Virg.