But the evidence of a deterrent effect is thin. An unpublished analysis of F.B.I. crime data from 1970 to 1998 by Anup Malani, a law professor at the University of Chicago, found that the presence of the felony murder rule had a relatively small effect on criminal behavior, reducing the number of deaths during burglaries and car thefts slightly, not affecting deaths during rapes and, perversely, increasing the number of deaths during robberies. That last finding, the study said, “is hard to explain” and “warrants further exploration.”

The felony murder rule’s defenders acknowledge that it can be counterintuitive.

“It may not make any sense to you,” Mr. Rimmer, the prosecutor in Mr. Holle’s case, told the jury. “He has to be treated just as if he had done all the things the other four people did.”

Prosecutors sought the death penalty for Charles Miller Jr., the man who actually killed Jessica Snyder, but he was sentenced to life without parole. So were the men who entered the Snyders’ home with him, Donnie Williams and Jermond Thomas. So was William Allen Jr., who drove the car. So was Mr. Holle.

Mr. Holle had no criminal record. He had lent his car to Mr. Allen, a housemate, countless times before.

“All he did was go say, ‘Use the car,’ ” Mr. Allen said of Mr. Holle in a pretrial deposition. “I mean, nobody really knew that girl was going to get killed. It was not in the plans to go kill somebody, you know.”

But Mr. Holle did testify that he had been told it might be necessary to “knock out” Jessica Snyder. Mr. Holle is 25 now, a tall, lean and lively man with a rueful sense of humor, alert brown eyes and an unusually deep voice. In a spare office at the prison here, he said that he had not taken the talk of a burglary seriously.

“I honestly thought they were going to get food,” he said of the men who used his car, all of whom had attended the nightlong party at Mr. Holle’s house, as had Jessica Snyder.