For nearly 34 years the murder case of 80-year-old Mar Vista resident Alice Lewis remained without any suspects.

Los Angeles police detectives said they finally received a break in the case in September 2009 when DNA evidence collected at the scene led to the arrest of then 50-year-old Dennis Vasquez in connection with the December 1975 rape and murder of Lewis. Investigators had determined that Lewis, who was found dead at her home in the 3500 block of Meier Street, was murdered by suffocation and the motive appeared to be sexual in nature.

Vasquez, who was 17 at the time of the crime, was charged by the county District Attorney’s Office with one count of murder, with special circumstances for rape and robbery, police said.

Now, more than a year after the arrest of Vasquez at his downtown Los Angeles-area home, Los Angeles Police Department Cold Case Homicide Unit detectives have identified a second man suspected of being involved in the killing of Lewis. Detectives said that as they continued their investigation, they became suspicious that Vasquez allegedly did not act alone.

Based on additional forensic analysis of the crime scene, detectives said they established probable cause to believe that Kevin Michael Shanahan was also allegedly involved in the murder of the elderly woman. The county District Attorney’s Office filed murder charges Dec. 12 against Shanahan, who was located in law enforcement custody in Minnesota, police said.

LAPD Det. Tim Marcia, a lead investigator in the cold case, said detectives surmised there was a second suspect based on unidentified fingerprints discovered at the home and statements that Vasquez made during an interview. He noted that the investigation is ongoing and police believe there could possibly be a third suspect.

Marcia declined to explain how Shanahan, who was 15 in 1975, was identified as a suspect but said police have learned that he and Vasquez were close friends who went to school together at the time and they both lived within close proximity to Lewis. Police allege that Shanahan was an active participant in the burglary at Lewis’ home and was present when she was killed, Marcia said.

The cold case detective credited the work of law enforcement officials and current technology in helping to track down another suspect in the 35-year-old murder.

“It’s rewarding in the sense that the department and the city of Los Angeles have given us the tools to go back on these types of cases,” Marcia said.

“It shows that technology is coming a long way and this is a prime example of that working.”

Marcia said he has not yet been able to contact a grandson of Lewis to inform him of the second arrest. Following the arrest of Vasquez, Marcia noted that the grandson was thankful that “no one forgot about his grandma.”

Police involved in the cold case highlighted the critical role of DNA evidence in leading to the arrest of Vasquez after 34 years. Detectives had determined in 2003 that biological evidence collected during Lewis’ autopsy could be tested for DNA, and a profile was stored in a DNA data bank, Marcia said. Vasquez was arrested after cold case detectives determined that a DNA sample taken during a prior arrest for a traffic violation allegedly matched evidence from the Lewis murder scene.

While Vasquez was a juvenile at the time of the crime, a district attorney spokeswoman said prosecutors asked to have the suspect tried as an adult due to the brutal nature of the case. Marcia said the Vasquez case has been approved for the adult court and a preliminary hearing has not yet been scheduled.

Shanahan, who had served time in federal prison for a bank robbery conviction, was located in police custody in Olmstead, Minn. following a parole violation, Marcia said. The suspect was awaiting extradition to Los Angeles County, where prosecutors will seek to try him as an adult in connection with the Lewis murder, the detective said.