A bouncer accused of sexually assaulting and murdering a young graduate student was framed by his employer in a cover-up that reached as high as the former mayor of New York City, a defense attorney told jurors Tuesday.

The employer, Danny Dorrian, came from a wealthy family with friends in high places. Defense attorney Joyce David said he accidentally killed Imette St. Guillen after a night of sexual domination play where she was bound and gagged, and then asked his family for help.

David suggested Dorrian, his family and his friends, who included an adviser to then-presidential candidate Rudy Giuliani, chose to lay the blame on her client, Darryl Littlejohn.

Dorrian has denied having anything to do with St. Guillen's killing. A prosecutor called David's accusation "the rankest kind of speculation."

St. Guillen was last seen alive on Feb. 26, 2006. Her nude body, bound and with a sock shoved down her throat, was discovered the next day on a roadside in Brooklyn wrapped in a quilt. She had been sexually assaulted.

Littlejohn pleaded not guilty to first-degree murder in her death.

In closing arguments Tuesday, his attorney placed the blame squarely on Dorrian. She said police zeroed in on Littlejohn and failed to investigate Dorrian to protect the family and also so Giuliani would not be dragged into the scandal because of the family's ties to his adviser Tony Carbonetti.

"Darryl Littlejohn was the solution to all their problems: solving the city's biggest crime at the time, protecting Daniel Dorrian and also protecting Rudy Giuliani from another scandal," David said.

Dorrian testified for the prosecution. When prosecutor Kenneth Taub asked Dorrian if he had anything to do with her death, he replied, "Absolutely not." He also insisted he did not have sex with St. Guillen the night she was killed and has denied that he pointed the finger at Littlejohn.

The prosecution has argued that Littlejohn was a sexual predator who kidnapped a drunken St. Guillen, raped her and killed her before dumping her body.

"It is the rankest kind of speculation by the defense to suggest that there is evidence that Danny Dorrian did the killing," Taub said during his closing argument.

At the time of her death, St. Guillen was studying criminal justice at John Jay College in Manhattan. A friend demanded they take a cab home together after a night of drinking. But St. Guillen, a 24-year-old from Boston, set off for another bar. She was last seen at The Falls, which Dorrian managed and where Littlejohn worked.

Littlejohn already is serving a sentence of 25 years to life for kidnapping one of two other women victimized in what police say was a sexual assault spree. The most dramatic testimony came from the two women, who recounted their stories on the stand.