It looked like a clear-cut case of serial murder.

Robert Silveria, suspected member of a gang of railriding hobo killers with a penchant for white supremacy, told police in 1995 that he'd bludgeoned a dozen drifters to death with rocks and axes. But now the 37-year-old transient who calls himself "Sidetrack" has recanted his confession, turning what seemed an easy conviction into a more difficult case.

Silveria goes on trial in Salem, Ore., in March. His defense lawyer is expected to argue that he was able to give details of the murders because he looked on while other gang members did the killing.

But whatever the outcome, the trial will shine a spotlight on the loose-knit Freight Train Riders of America (FTRA), which was started by Vietnam veterans in the early 1980s and now numbers from 1,000 to 5,000 members, according to police. Although some members have denied the gang is white supremacist, investigators say otherwise.

"If you're a black or Hispanic and you get on a train with an FTRA member, you don't get off alive," says Spokane police officer Bob Grandinetti, a leading expert on the FTRA. "The days of the fun-loving, harmless hobo are over."

Police believe the FTRA may be responsible for hundreds of deaths, beatings and thefts along railroads in the past 15 years. The FBI briefly investigated the gang for involvement in the 1995 derailment of an Amtrak train near Phoenix, according to a memo from the security division of Burlington Northern.

It's unclear what role white supremacy plays in the gang. Graffiti left by members include swastikas and Nazi lightning bolts. But without question, police say, gang members are violent.

Grandinetti says most carry knives and axe handles they refer to as "goonie sticks." Officials have identified a "Goon Squad" within the gang that is responsible for many violent attacks.

Member Douglas Castle was convicted of the 1995 murder of a fellow transient in Montana who had insulted the FTRA. And others have been convicted in numerous assaults and other crimes.

Grandinetti began his probe in the 1980s after railroads began reporting bodies in boxcars and by tracks. Between 1990 and 1992, 10 bodies were found in Washington and Idaho, their shirts pulled up and trousers pulled down.

Since then, Grandinetti has collected dossiers on 800 FTRA members, most of them white men, by befriending the railriders or visiting their nighttime booze and methamphetamine parties.

Michael Quakenbush, a detective in Salem, Ore., ran across Robert Silveria's name while investigating two 1995 railroad homicides. Quakenbush interviewed Silveria over five days, during which Silveria allegedly confessed to killing 12 people, including a college student and an accountant.

In a letter to a former cellmate, Silveria purportedly explained why he selected homeless transients: "I preyed on the weak."

Now, law enforcement agencies are intensifying investigation of the FTRA. Federal agencies including the FBI, which led a July 1996 conference on the gang, are looking into the Silveria case and others, police say.

"The FTRA didn't get attention because the victims were people no one cared about or even knew," Grandinetti says. "When there were investigations, they usually came up with zero because these people are so transient. Now, the heat's really been turned up."