FORMER teen heart­throb DAVID CASSIDY is on a crash course with self-destruction, and friends fear he’ll be dead within three months if he doesn’t get his boozing under control.

After the “Partridge Family” star was arrested for his third DUI in a little more than three years on Jan. 10, those close to him don’t believe rehab is the answer – they think David’s only hope now is a stint in the slammer!

“David’s hell-bent on killing himself, and if he doesn’t get help fast he won’t survive another three months,” an insider revealed. “He’s risking everything, but he doesn’t seem to care enough to quit drinking.”

David, 63, was first arrested for driving under the influence in 2010 in St. Lucie County, Fla. In August, he was picked up again, this time in upstate New York.

In an exclusive interview, David’s “stepdad,” Marty Ingels, told The ENQUIRER: “He got off easy the last time around. On the second DUI, he got some fancy lawyer and it was reduced from a felony to a misdemeanor.

“This third DUI, believe it or not, actually changes the status of that second one. It brings it back up to a felony.

“So now he’s in real hot water!”

Marty, 77, who married David’s stepmom Shirley Jones in 1977, continued: “A lot of the family is praying that David goes to jail because they believe it’s the only way he can save his life.

“I think they feel David is too far down the road to addiction and alcoholism for rehab alone to help him anymore. Jail would be a godsend. David needs at least 120 days behind bars.”

Marty says Shirley, who helped raise David after marrying his father, Jack Cassidy, in 1956, is not surprised by her stepson’s struggles with the bottle.

“She lived through this kind of alcoholic behavior with David’s dad,” explained Marty.

Jack Cassidy died on Dec. 12, 1976, after passing out and dropping a lit cigarette in his Los Angeles apartment. His body was burned beyond recognition.

“That’s the same direction David’s headed in, sadly,” said Marty. On Jan. 10, David was pulled over for making an illegal turn near the Los Angeles airport. The officer noticed the smell of booze coming from David’s car, according to a California Highway Patrol press release. David then blew a .19 on a Breathalyzer test – more than twice the state’s legal limit.

David, whose daughter is “Arrow” star Katie Cassidy, has been going through a rough spell lately. Not only is he facing financial trouble, he and his third wife, Sue, split up. She’s moving from their home in Fort Lauderdale, Fla., to Los Angeles to be near the couple’s 22-year-old son, Beau.

Since this DUI is David’s third strike, he could potentially be facing time behind bars. But that may be a good thing in the long run.

“He’s lost everyone. There’s nothing really left for him,” Marty added. “Maybe jail will be his savior.”