Investigators used DNA found on a conch shell used as a murder weapon to charge David Reed with the murder of his half-sister, Rosie Moniz.
Ms Moniz was found murdered in her room in 2001 having been beaten to death. Her murder went unsolved for 20 years, and her parents have since died not knowing who killed their daughter or why.
The Bristol County District Attorney's office announced the charges on Thursday.
Mr Reed's DNA was found inside the bloody conch shell that he allegedly used to beat Ms Moniz to death. According to investigators, Mr Reed allegedly gripped the inside of the shell for a better grip while attacking his half-sister. His DNA was then left inside the shell.
WCVB reported that Mr Reed provided the DNA when he was charged with another assault. In that case he allegedly beat another woman with a tire iron and left her to die, and then assaulted a New Bedford police officer.
The assault resulted in a conviction, and Mr Reed was imprisoned, during which time he had to provide a DNA sample.
The district attorney claimed that the motive in the murder was simple robbery. Mr Reed was arrested in September.
"Motive appears to be robbery. Her purse was disturbed. It was dumped. The contents were dumped out. Money was taken," Bristol County District Attorney Tom Quinn said.
According to the outlet, Ms Moniz's father discovered the woman's body.
"My mother and father aged overnight, you could see it," her brother, Paul Cunha, told the broadcaster. "It was really tough."
Mr Cunha revealed that Mr Reed was a pallbearer at Ms Moniz's funeral. He described Mr Reed as "very quiet, unusually quiet," at the funeral, and said he disappeared "pretty much after that."
After Mr Reed was released from prison on his assault charge, he disappeared until he was arrested in Rhode Island.
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