A single shred of physical evidence is all that's needed to link the murder of Imette St. Guillen to bouncer Darryl Littlejohn, a parolee whom cops have focused on because of a raft of circumstantial evidence.

"He is a suspect," a detective close to the case told the Daily News. "He is our only suspect."

Police hope to get back DNA evidence as early as today. At the top of the list is skin found under St. Guillen's broken fingernails - believed to be scratched off as she fought her attacker, police sources said.

"If we could charge based on circumstantial evidence, he would be charged already," a police source told The News.

The 41-year-old ex-con was sent to Rikers Island yesterday for violating his parole by breaking curfew and failing to disclose he was working as a bouncer.

The violation could keep him locked up for 90 days.

Investigators hope the minivan seats found stashed in Littlejohn's 121st Ave. home in Jamaica will provide the physical evidence they so desperately need.

Detectives believe St. Guillen, 24, was taken in a van to a desolate street in East New York, Brooklyn, where her battered body was dumped Feb. 25. She had been raped and tortured. Her face was covered with tan tape.

The seats found in Littlejohn's apartment had been removed from a gray Windstar minivan that cops found parked a few blocks from his home. Detectives hauled off the vehicle about 9:20 last night.

About an hour and a half later, they towed a second van, a dark blue Dodge Ram with curtained windows, from the home's driveway.

Police sources said the investigation had been hobbled by the selfish actions of Manhattan barkeep Daniel Dorrian - whose brother Michael owns The Falls, a Lafayette St. pub where St. Guillen was last seen alive.

Dorrian allegedly gave cops misleading information about St. Guillen's final minutes in The Falls, potentially giving the killer a week to destroy or hide damning evidence, sources said.

"He's a man with no conscience whatsoever," a police source said of Dorrian.

Dorrian first told cops St. Guillen left the pub alone around its 4 a.m. closing time. He changed his story over last weekend, telling cops he had ordered Littlejohn to escort a drunken St. Guillen out of the bar, sources said.

Dorrian and other employees also finally told cops they heard St. Guillen and Littlejohn arguing after the two left the bar through a secret side exit.

"They heard yelling. More angry yelling, not fear," a source said. "No one called out for help or said they were being attacked."

St. Guillen was upset that she was being ejected from the bar before she could finish her drink, the source said.

A man at The Falls who identified himself as "Danny the manager" told The News last week he did not remember seeing St. Guillen.

"She could have been a credit card customer. We have hundreds of customers paying with credit cards," Danny said. "I just hope they catch this guy. I just hope I have a job after this."

Dorrian's lawyer Daniel Connolly, a founding member of former Mayor Rudy Giuliani's law firm, Giuliani Partners LLC, did not return calls yesterday.

Littlejohn's DNA has been on file with state authorities since he was convicted of a bank robbery in 2000. He was on state parole and federal probation. Littlejohn has denied involvement in the slaying to The News.

Along with tests on the skin under St. Guillen's fingernails, cops are waiting for forensic investigators to tell them if DNA was found in a stain on the floral blanket wrapped around her.

Cat hairs on the blanket and the packing tape wrapped around her face also could provide clues.

Sources said Littlejohn was put in lineups yesterday for other unsolved sexual assaults, but no victims picked him out. Last night, cops removed additional evidence from his home, including clothing and stained pieces of carpet. Cops also took socks to see if they match the tube sock shoved down St. Guillen's throat.

St. Guillen's mother, Maureen, and sister Alejandra told The News they have tried not to get swept up in the probe.

"That's the only way we can handle it right now - not knowing, not seeing," her mom said.

"We can't imagine going through the up and down and the theories," her sister added. "Until there's an arrest, there's nothing."