He said co-defendant Richard Beasley, 53, of Akron, who has pleaded not guilty and will be tried separately, reminded Rafferty during the drive home after the first killing that he knew where Rafferty's mother and sister lived.
Asked what would have happened if he had objected, Rafferty responded, "He probably would have murdered me right there in the car."
Authorities say the victims answered Craigslist ads for work on a nonexistent cattle farm in rural Noble County in southeast Ohio. The scheme targeted older, single, out-of-work men with backgrounds that made it unlikely their disappearances would be noticed right away, according to authorities.
Beasley could face the death penalty if convicted. As a juvenile, Rafferty cannot and instead faces a life prison sentence without chance of parole if convicted of aggravated murder.
Rafferty said the horror of the first killing as the victim interviewed for a job at a southeast Ohio farm surprised him and, as he and Beasley drove home, Rafferty testified that he vomited during a rest stop.
"Did you agree to any of this?" defense attorney John Alexander asked.
"No," Rafferty responded as his tearful mother watched from the front row.
"Did you want to be a part of it?" his attorney asked.
"No," Rafferty said.
After the first killing, Rafferty testified, Beasley stayed in touch, sometimes daily, to check on his whereabouts, and Rafferty said he was afraid.
"Did you fear he was watching?" his attorney asked.
"Yes," Rafferty responded. "Because he was."
Rafferty, dressed in a gray open-collar jersey and green slacks, described a one-parent upbringing, seeing his drug-addicted mother only occasionally and often alone at home as his father worked.
His father befriended Beasley, and the ex-convict took Rafferty under his wing, taking him to church and becoming a "spiritual mentor," Rafferty testified.
On the first outing of what led to three shooting deaths and the wounding of a fourth man, Rafferty said there was no warning on the killing of Ralph Geiger, 55, of Akron, on Aug. 9, 2011.
Geiger, who was killed the day after he left a homeless shelter, saying he was taking a farm job, was shot by Beasley without notice as they walked through a wooded area, ostensibly looking for a path to a farm, Rafferty testified.
In one second Beasley pulled out a pistol, and in another shot Geiger, Rafferty testified. "I said to myself, 'Oh, my God,'" the teenager testified.
Rafferty said there was no logic to the killing, leading him to believe he might become the next victim.
"I was terrified," Rafferty testified.
Asked by his attorney why he accompanied Beasley on subsequent killing outings, Rafferty replied it was "that or die."
Under cross-examination, Rafferty acknowledged he had chances to report the alleged triggerman to police but never did so. He said he had a shotgun and a cellphone but never called police or told anyone about the slayings.