A man already punished for his role in a robbery will likely plead guilty Wednesday and be imprisoned for the same heist after failing to reveal details of Brittanee Drexel's disappearance from Myrtle Beach in 2009, his attorney said.

A jailhouse informant had accused Timothy Da'Shaun Taylor and his father of kidnapping, raping and killing the 17-year-old New Yorker before dumping her body in a McClellanville-area alligator pit.

After Taylor's name emerged, federal authorities discovered that he had been sentenced to probation for acting as a getaway driver in a 2011 robbery of a McDonald's. Dubbing the penalty unfair compared with his accomplices' state prison terms, prosecutors had Taylor indicted on three federal charges.

But another reason, authorities have acknowledged, was to elicit information from Taylor in hopes of solving Drexel's suspected abduction. Her fate remains a mystery. Her body was never found.

Both state and federal governments can charge someone in the same incident under an exception to the "double jeopardy" rule, which generally bars someone from being prosecuted twice.

Taylor, a teenager when Drexel went missing, has insisted that he was attending class at Lincoln High School when she was supposedly slain.

But the prosecution put him in a lose-lose situation, defense attorney Mark Peper argued. Taylor, now 26, is expected to plead guilty in an agreement that would call for 10 to 20 years behind bars. He had no way to fight the case because he had already admitted to the robbery.

"There's nothing more we can do to assist the FBI investigation," Peper said. "We told them everything we know. They put the squeeze on him, but it wasn't fruitful. ... He's frustrated that he doesn't have the ability to help himself out."

A hearing at 1 p.m. Wednesday in U.S. District Court in Charleston is bound to be unusual. His attorneys will likely ask for the charges to be dismissed under "double jeopardy" provisions. But the motion is expected to fail, prompting his plea during the same proceeding. Judge David Norton will sentence him later.

For years, FBI agents have chased down leads from Myrtle Beach to the McClellanville area.

Drexel traveled to the Grand Strand during spring break. She was captured on video camera at the Blue Water Hotel on April 25, 2009. Then, she vanished.

Years passed before an inmate in Georgetown County told the FBI that he had seen Taylor and his father with Drexel at a McClellanville-area "stash house."

The informant alleged that Taylor was sexually abusing Drexel, who then escaped, an FBI agent testified last year. Two gunshots rang out, and the tipster assumed that Taylor's father, Timothy Shaun Taylor, had killed her, the agent said.

Her body was thrown into a pit to be eaten by gators, the informant alleged. Authorities would later search almost 40 ponds, but her body was not found.

Two years after Drexel's disappearance, the younger Taylor was jailed in the McDonald's robbery in Mount Pleasant.

Federal prosecutors said he orchestrated the September 2011 holdup but stayed in his car while two other men went inside. A robber who shot and wounded the manager was later sentenced to 25 years in prison, while the other man got six years. Taylor spent two years on probation.

In a court filing this week, Assistant U.S. Attorney Jim May said Taylor's penalty was "far below" the others. An attempt to reach May for further comment was not successful.

As Taylor's probation ended last year, he was indicted on three federal counts: robbery, obstructing interstate commerce by robbery and using a firearm in a violent crime.

The gun charge carries between 10 years and life in prison. The others carry no minimum terms.

Peper said prosecutors would not drop the firearms count unless Taylor agreed to between a 10- and 20-year sentence. Faced with more time if he had gone to trial, Taylor approved the deal, Peper said.

"Our hope was that the court would see through this," Peper said. "But he is essentially at peace with the fact that he's going to have to go to prison."

Reach Andrew Knapp at 843-937-5414. Follow him on Twitter @offlede.

Andrew Knapp is editor of the quick response team, which covers crime, courts and breaking news. He previously worked as a reporter and copy editor at Florida Today, Newsday and Bangor (Maine) Daily News. He enjoys golf, weather and fatherhood.