Kesha -- Dr. Luke Says She Lied to Save Her Ass Over Sandy Hook

4:20 PM PST -- Kesha's lawyer Mark Geragos tells us ... "All these claims show is a predator attempting to deflect attention from the real facts -- that Kesha was mentally and sexually abused by Luke for years."

He adds, "All of Luke's recent filings bare no consequence in this case and are a sad attempt to paint Kesha -- his victim -- in a negative way."

Dr. Luke is keeping the heat on Kesha, saying he has more proof she's a liar ... and this time it involves the tragedy at Sandy Hook.

Luke filed legal docs -- trying to discredit her claim that he drugged and raped her when she was 18. He says she flat-out lied when she told the public he forced her to sing "Die Young" to distance herself from the massacre. Luke says she also lied by saying he wrote the song.

Luke claims Kesha "proudly, and truthfully" took credit for the lyrics before the Sandy Hook shootings.

He also put in the legal docs a story that has circulated ... that Kesha insinuated her dad was Mick Jagger. He says she knows that's a lie but it never stopped her.

And Luke isn't limiting his attack to lying ... he says she's a horrible person who once locked her mom out of a Vegas hotel room with no shoes and no money. Luke says, "Pebe was forced to wander the hotel's casino floor, begging for assistance."