A jury deliberated for nine hours over whether Jeffery Martin Young (right), shown with attorney Neil Horn, was responsible for a man's death. The not guilty verdict came in late Thursday.

A circumstantial case against Jeffery Martin Young was not enough to prove he was the hit-and-run driver who killed a lawyer out for an early morning run, a Roanoke County jury decided Thursday night.

The jury acquitted Young of hit-and-run and involuntary manslaughter -- leaving the question of who killed Thomas Farrell as much a mystery today as when police first began searching for a suspect a year and a half ago.

The verdict came at 10:45 p.m., after nearly nine hours of deliberations.

With no eyewitness testimony and scant physical evidence connecting Young to the crime, prosecutors relied on an entirely circumstantial case.

Young was spotted multiple times driving around the Southwest Roanoke County neighborhood where Farrell was hit while jogging the morning of Jan. 28, 2008. Witnesses also recalled seeing Young's white Jeep Wrangler -- with heavy damage to the front end that wasn't there in the hours before Farrell's body was found.

But there was little more to the case than that, defense attorney Neil Horn said.

Young, a bearded and long-haired man with a history of mental illness, did not testify. He let out a quiet sigh after the jury's late-night verdict.

In fact, the only witness for the defense was a biomechanical engineer who challenged Commonwealth's Attorney Randy Leach's theory that dents on Young's jeep were consistent with the injuries found on Farrell's body.

Ralph Aronberg appeared in Roanoke County Circuit Court via a videoconference link from his office in Fort Lauderdale, Fla., where he operates a firm that specializes in traffic accident reconstruction. Aronberg testified that there were no fabrics, blood or tissue found on the Jeep -- evidence needed for a valid scientific conclusion.

His testimony differed from that of Jason Kerrigan, a University of Virginia scientist who testified for the prosecution Wednesday. Kerrigan testified that while he could not conclusively say that Young's Jeep struck Farrell, the damage it sustained was consistent with the injuries suffered by the 49-year-old lawyer.

Farrell, an avid jogger, was found lying on the side of Springlawn Avenue with a massive fracture to the back of his skull, broken ribs and abrasions to his side.

Aronberg cast doubt on the prosecution's theory that a dent on the Jeep's hood was caused by Farrell's head during the collision. Farrell was 5 feet 9 inches tall, Aronberg testified, which put his center of gravity below the top of the Jeep's hood. That means the force of the impact would likely have thrown Farrell forward, not up and onto the hood of the Jeep, Aronberg told the jury.

But in the battle of expert opinions, Leach argued that Kerrigan was the more convincing witness -- noting that the college professor could teach some of the seminars that Aronberg relied on for his training.

Leach also pointed to testimony from witnesses who said they saw Young pouring water on his Jeep in the parking lot of the County Store on Starkey Road after the discovery of Farrell's body. That was an attempt to remove any evidence that might have been on the Jeep, the prosecutor argued.

Yet no debris from the Jeep was found at the spot where Ferrell was struck.

Long before the prospect of a hung jury emerged, the panel's deliberations were challenged.

Horn asked for a mistrial after it was discovered that an improper piece of evidence -- which included newspaper clippings and other reports of a second hit-and-run charge that Young faces in Floyd County -- was mistakenly sent to the jury room for their consideration along with the rest of the exhibits.

Horn had earlier introduced the binder full of documents outside the jury's presence in what turned out to be an unsuccessful effort to have the trial moved out of Roanoke County because of the high media attention it garnered.

Later in the trial, Judge William Alexander ruled that prosecutors would not be allowed to bolster their case against Young by mentioning the Floyd County charge.

Two jurors said they read some of the accounts before the panel realized what they were and alerted the judge.

"At this point, we have at least two people who have been tainted in the jury room," Horn said.

But Alexander took Horn's motion for a mistrial under advisement after the jurors assured him they would not consider what they had seen.

In the end, Horn argued, the 30-some witnesses who testified for the prosecution about Young's presence in the area for days was not enough to overcome the lack of a single person who witnessed the actual incident.

"The commonwealth can bring 10, 20, 30 or 40 people in here to say we saw Jeffrey Young here, there and all over," Horn said. "But that doesn't have any bearing on what happened on Springlawn Avenue."