Prosecutors and police are crediting the indictment of a DNA sample with the capture of a man who allegedly ejaculated on a woman while on a Green Line train eight years ago.
Timothy Day, 52, of Maryland, pleaded not guilty in Suffolk Superior Court yesterday. He was charged with indecent assault and battery.
Authorities said Day and the woman were riding a B train crowded with Red Sox fans on their way to Fenway Park in 2004. The woman, then 23, said she felt a man with an erection standing behind her.
The man fled before the woman was able to identify him and she then noticed a white liquid running down her leg and on her purse.
"She went home and washed her pants," said Tara Burdman, an assistant district attorney. "The next morning she notified Transit Police who recovered her bag."
The bag was given to the Boston Police Crime Lab, which identified the liquid as semen.
A database revealed the DNA was the same in a similar 2002 attack on a train in Washington, D.C., but the man was unknown in that attack as well.
Prosecutors from Suffolk County District Attorney Daniel Conley's office in 2005 indicted the DNA associated with the attack as "John Doe."
Last year, authorities received a database match on the DNA after Day was convicted of a federal crime and required to submit a DNA sample.
Day was arrested by Metro Transit Police last week and turned himself in to police yesterday for the B train attack.
"This new science has proven to be another useful tool," said Transit Police Deputy Chief Lewis Best. "The riding public should know we will use whatever means possible to identify and apprehend and prosecute criminals that engage in this type of behavior."