Doug Martin's Family Files Wrongful Death Lawsuit

Doug Martin's family claims excessive force by police played a "substantial" role in his death last year ... and they're taking the matter to court.

Douglas and Leslie Martin filed a lawsuit against the city of Oakland, responding officers, and an ambulance company this week ... saying they want to get to the bottom of exactly what happened to their 36-year-old son back on October 18.

"Unfortunately the litigation is a mechanism to best get that done," attorney John Burris said.

At the time, Oakland PD said Martin was involved in a break-in and died after he became unresponsive during a brief struggle with responding officers. Martin's family said he was experiencing a mental health crisis at the time of the incident.

Body camera and surveillance footage was released earlier this year ... showing officers restraining Martin after tracking him down. The clip shows a struggle, but several minutes of video were not released.

In the lawsuit, Martin's family stated the former Tampa Bay Buccaneers running back was held face down as officers pressed on his back, and they believe that the restraint contributed to his death. When officers turned him on his side, the suit noted how they thought he was either sleeping or pretending to be ... and only called for medical help after he remained unresponsive.

The family is also taking issue with paramedics, claiming they took more than 15 minutes to respond to the call ... and did not rush to provide medical care once they got to the scene.

The initial autopsy results have not been released ... as the family requested further review. Burris stated a second autopsy was also conducted, and a pathologist determined, for now, that restraint asphyxiation was the cause of death.

Burris revealed Martin's family sent his brain to the Boston University CTE Center ... but noted the disease might explain his behavior that night, but not his death.