The day Thomas dropped the cigarette he was apearning in court on an unrelated charge. The cops assigned to trail him, and watched as he discarded a cigarette on the sidewalk in front of the courthouse. Cops then picked up the butt and tested it for DNA.
The DNA on that butt, would eventually land him in front of a judge in the same courthouse, charged with one of the most egregious patterns of serial rape in decades.
Thomas will likely be tried in Connecticut first before being extradited elsewhere to stand trial.
Prosecutors in Virginia say he is facing six rape counts, which each carry a maximum sentence of life in prison.
"This case concerned me almost as much as DC sniper case," said Paul B. Ebert, the prosecutor for Prince George's County, Va. "It was music to my ears to hear he had been arrested."
Known for stalking his victims and attacking them with weapons as diverse as guns and broken bottles, authorities also tried finding the rapist by comparing the DNA he left at crime scenes to that of family members whose DNA had been tested by police.
The last known attack attributed to the suspect took place in 2009, when two 17-year-old girls were raped at gunpoint after returning from a night of trick-or-treating in Prince William, Va. A third girl was able to escape and contact her mother with a cell phone. The rapist escaped as cops closed in on him.
All of the attacks occurred at night and near major highways. The first known rape occurred in Maryland.
From there, the rapist left a trail of terror and DNA along the Eastern Seaboard to Virginia, then to Connecticut and Rhode Island, before making his way back to Virginia.
Authorities said the rapist stalked and studied his victims, apparently attacking them in neighborhoods he knew well. He knew when they were most vulnerable, such as when they were home alone with their children or had failed to lock windows or doors, investigators said. "He's like a lion looking for prey," one of his victims, a woman who was raped in her Leesburg, Va., apartment in 2001, told the Washington Post.
The rapist wielded a handgun or a knife in several attacks, a screwdriver and broken bottle in others. After some assaults he left feces near the crime scene.
In August 2009, law enforcement officials in Virginia began efforts to use familial DNA in the search for the rapist. That effective, yet controversial method identifies suspects through the DNA of a close blood relative who already has been in the criminal justice system after being arrested or convicted.
ABC News' Don Ennis contributed to this report.