Authorities never expected fugitive rapist Andrew Luster to last very long on the lam.

"He didn't have the background that enabled him to do that," said Robert Mack, the supervising special agent in Ventura County FBI office. "He grew up as someone who didn't have to hold a job. It's difficult for someone in that lifestyle to think about 'Oh, now I'm now a fugitive' and 'How do I keep law enforcement away?' "

So now, even though Luster is in prison, the investigation into his flight from justice is continuing. Most likely someone helped Luster evade police, and authorities want to bring that person in.

"We're certainly interested in unraveling the mystery of who helped Mr. Luster and how," said Maeve Fox, a Ventura County senior deputy district attorney, "and when we do that ... we will work in conjunction with federal authorities to convict whoever is so deserving."

Assisted by Ventura County sheriff's deputies and the District Attorney's Office, FBI agents in Mexico and Southern California are retracing Luster's steps from the time he cut off his electronic monitoring bracelet nearly six months ago to his re-apprehension Wednesday after he was picked up by a bad-boy bounty hunter in Puerto Vallarta.

Luster, 39, of Mussel Shoals was first arrested in July 2000 when a Santa Barbara woman reported that he had drugged and raped her. More women quickly came forward. Luster was out on bail when his trial began in December. Before it was over, he had fled. The jury convicted him of 86 counts related to drugging and raping three women and videotaping the attacks. He was sentenced to 124 years in prison.

Since his escape, Luster has been hunted by FBI, Ventura County sheriff's deputies, and bounty hunters. At least part of the time, he'd been living in a $30-a-night-Mexican motel with surfboards and a video camera in his room. Wednesday, he was getting a taco from a street stand when Hawaiian bounty hunter Duane "Dog" Chapman tackled him. Mexican police caught up with Chapman, his crew and Luster, as they drove away in an SUV. All of them were taken into custody. Bounty hunters can't legally operate in Mexico.

Authorities don't think Luster got that far on his own.

"Driving down to Mexico is no big deal, but what do you do when you get there? How do you live? Everything now is tracked and traceable," Mack said. "A person who is not experienced in obtaining a false ID would have a difficult time to remain a fugitive for a long period of time; so the logical thought process is someone may have been helping him."

Mack and Ventura County Sheriff's Department spokesman Eric Nishimoto declined to name specific suspects.

"It would be difficult for any individual to escape like he did without some type of help," Nishimoto said. "It's certainly a possibility we will find someone who was involved."

Federal charges are possible. Fox said other possible charges include "being an accessory after the fact" or "obstruction of justice."

"Prison is definitely a possibility," she said. "It is felony behavior."

Just giving the guy a sandwich, though, probably wouldn't land someone in the slammer.

"It would have to be conscious and egregious activity," Mack said. "More than just him showing up at your doorstep and saying 'Can you hold my bags for a few weeks?' "

Mack said this kind of after-the-fact investigation is fairly routine.

"Just as in any type of crime committed: bank robbery, carjacking," Mack said, "you not only look at people who initiated the crime, but you also look at people who helped them commit the crime or cover it up."

In this case, it will probably be a matter of doing interviews and following the "paper trail," Mack said.

"You just think logically," Mack said. "You are going to spend money and make phone calls, and that's the way you would normally retrace steps."

Although neither Mack nor Nishimoto could give a definite time for completing the investigation, Nishimoto said, "It can't take too long."

When it's over, Luster could have company.

"I hope there are some people out there getting sweaty brows now," Fox said, "and perhaps didn't sleep too well last night."