Lawyers for survivors of a couple killed in a 2016 car crash will attempt in a lawsuit to prove what a criminal investigation could not: that a nurse who’d just gotten off an overnight shift was impaired by controlled substances when he ran a red light.

A 202-page Palm Beach County Sheriff’s report on the 2016 crash west of Delray Beach that killed Andre and Vivian Brito says investigators found in Raymond Joseph Kelly’s vehicle envelopes and vials containing more than 300 tablets of medications. And that he showed signs of being under the influence of narcotic painkillers.

But by the time sheriff’s investigators arrived, the report said, emergency workers already had given the badly hurt Kelly medication for pain, and because of that, a sheriff’s forensic expert later "could not say with any certainty" whether Kelly was impaired at the time of the collision. Because of that, "these were the only charges I was able to file," Palm Beach County Sheriff’s homicide investigator Kurt Kloepping told Palm Beach County Circuit Judge Paul A. Damico at a July 26 traffic hearing at the South County Courthouse.

At that hearing, the judge ordered that Kelly, now 67, of Royal Palm Beac, pay $1,000 in fines for three traffic tickets — failing to use a designated lane, running a red light and careless driving — and lose his license for six months. Vivian Brito’s sister, Patricia Da Silva, said just after the hearing that "justice wasn’t applied." And her lawyer said a civil suit was in the works.

That complaint, which attorney Adam Langino said his firm filed Thursday in Palm Beach County Circuit Court, says Kelly "operated his motor vehicle under the influence of controlled substances to the extent that his normal faculties were impaired."

"It is our hope that we will be able to gain a better understanding as to why Kelly ran the red light, ultimately killing Andre and Vivian, and to hold him accountable for his actions," Da Silva, said Thursday in a statement. And Langino said that "the police investigation was able to show what happened but not why it happened. He added that "the family and children still do not have closure."

The crash made orphans of brothers Rafael Brito, then 11, a sixth-grader at Lake Worth Christian School, and Lucas, then 17, who would graduate three months later from Park Vista High School in suburban Boynton Beach.

Kelly’s attorney, Douglas Duncan, said Thursday he had no comment. Duncan said at the July court hearing that Kelly, who is married and has a young son and was on medical leave, is "remorseful" about the fatal crash.

Watch: Lucas Brito reflects on his late parents in 2016

Witnesses told investigators that at about 8 a.m. on March 1, 2016, Kelly cut into a right-turn-only lane and ran a red light just before his car slammed into Andre Brito, 41, and Vivian Leal Brito, 39, who lived west of Lake Worth. The Britos were Brazilian nationals who later became U.S. citizens along with their children, elder son Lucas told The Post in May 2016.

After the crash, Kelly was taken for treatment to Delray Medical Center, the hospital where he worked as a registered nurse, and where he reportedly had finished a shift hours earlier. The report says members of Delray’s medical staff told investigators Kelly told them he had left work and could not remember the crash, "telling them that he fell asleep at some point." At the hospital, he was given fentanyl, a synthetic opioid 50 to 100 times more powerful than morphine that can be prescribed for severe pain.