Story highlights

Mari Gilbert says police mishandled investigation of deaths on Long Island, N.Y.

She says she believes her daughter was slain by a serial killer

She threatens to sue Suffolk County police if the case isn't handed over to the FBI

Shannan Gilbert's remains were identified Saturday

(CNN) —  

The mother of Shannan Gilbert said Tuesday that police botched an investigation into her daughter’s death and the apparent murders of other victims on Long Island, New York, and she threatened to file a lawsuit against Suffolk County Police if the FBI doesn’t take over the case.

The attorney for Mari Gilbert described Suffolk County’s serial killer investigation as “clownish” during a news conference in Oak Beach, where her daughter’s skeletal remains were uncovered last week.

“The investigation that’s taken place so far is comparable to something you’d find in Podunk County,” said attorney John Ray, who likened Police Commissioner Richard Dormer to the Pink Panther, a bungling French cartoon detective.

Since December, police have uncovered 10 other sets of human remains scattered across two Long Island counties, prompting competing theories of what led to their demise.

Ray on Tuesday accused Dormer’s office of violating the civil rights of the victims by inadequately investigating.

“He thinks this is some kind of a silly scene for the Suffolk County police to be involved in only because Shannan was an escort,” he said.

Neither Dormer nor Suffolk County Police were immediately available for comment about the allegations.

Gilbert, 24, vanished in May of last year, and the search for her led police to four female bodies seven months later. All four have since been identified, like Gilbert, as prostitutes who advertised online.

The bodies were found in various stages of decomposition, and additional remains were later uncovered in neighboring Gilgo Beach and in Nassau County, about 40 miles east of New York City.

On Saturday, a medical examiner identified Gilbert’s remains, uncovered after investigators drained swampland near Ocean Parkway on Oak Beach.

Ray says that because Gilbert – a resident of Jersey City, New Jersey – crossed state lines to visit a client in New York, the investigation should be federal.

Federal agents have joined Suffolk County investigators at least twice before, last announcing their assistance in April after searching 18 “spots of interest” across Long Island.

But Dormer’s office has largely remained the public face of the probe, and is thought to be leading the investigation.

“Today, I hope this brings us one step close to finding a killer,” the elder Gilbert told reporters Tuesday. “But we need help. We need help from the public. We need help from the FBI.”

Standing beside her attorney, Gilbert said she believes her daughter was murdered by a serial killer.

Police, however, have maintained that, unlike the other victims, Shannan Gilbert’s death is not thought to be the work of the suspected killer.

Top law enforcement officials publicly sparred over competing theories in the case last week during a county legislative hearing, exposing rifts between investigators in a case that’s garnered national attention and widespread scrutiny.

Dormer has said that he believes a single person is responsible for the alleged murders.

“The theory is now that we’re dealing with one serial killer,” he told reporters in November, reiterating his position during the hearing Thursday.

Moments later, in the same forum, Suffolk County District Attorney Thomas Spota took the stand and rejected the police commissioner’s statement in a move that seemed to punctuate the apparent discord growing between the two men.

“I very, very much disagree with that theory,” Spota said. “I don’t know of anybody who, in the police department, who is actively conducting the investigation who shares that theory.

“Quite frankly, I don’t know why there was a unilateral change in theories.”

In May, Spota told reporters that a new collection of human remains uncovered on a nearby stretch of Long Island beach were not believed to be connected to the first four victims.

Dormer, who initially told reporters the bodies could be the work of a killer or multiple killers, later pointed to similar dumping grounds as one common aspect of the investigation that supports the notion of a single killer.

Authorities have sifted through more than 1,000 tips related to the case. But it’s unclear whether that has shed any light on the investigation.