On July 1, David Desper showed his friend Justin Gualtieri a news story about an alleged road-rage murder in Chester County.

Then, Gualtieri would tell police, Desper started talking, confiding in his friend about what had happened three days earlier on a stretch of Route 100 southbound where two lanes merge into one.

"Woah, I really f—ed up, man," Gualtieri recalled Desper saying that night, according to police documents read in court Thursday.

Nearly nine months since Desper allegedly shot and killed 18-year-old Bianca Roberson in an apparent fit of rush-hour road rage, the Trainer man returned to a West Chester courtroom for a hearing at which prosecutors were tasked with proving that Desper's case should proceed to trial.

In doing so, prosecutors called to the witness stand two West Goshen Township police officers, who talked for the first time publicly about specific details of the case.

Desper's attorney, Daniel McGarrigle, pointed out that no witnesses told police they saw a gun go off on the highway that day, and only one motorist said he heard the sound of a gunshot. Therefore, he said, the evidence was circumstantial and did not prove Desper shot with intent to kill.

"There isn't a single witness that can state the manner in which the gun was fired," McGarrigle said.

"The reality is, when you shoot someone in the head, you don't really need to know how many shots were fired," said Assistant District Attorney Christopher Miller. "One shot, one kill. That's all it took."

County Court Judge Ann Marie Wheatcraft said a jury would get to hear those arguments at Desper's trial, which is set for May 21.

In a purple shirt and tie, the 29-year-old sat quietly. His black hair was combed to the side, and his right hand was unshackled so he could take notes. As he was brought in, Desper made eye contact with supporters — who filled one side of the small courtroom — but said nothing.

Across the aisle sat Roberson's family and friends. In the front row, her mother, Michelle Roberson, wept, at times dropping her head and clasping her hands. She left before the hearing was over. The teenager's father, Rodney Roberson, remained, intently watching the proceedings and occasionally wiping away tears.

On the stand, West Goshen Detective Jose Torres and Sgt. Darren Sedlak revealed several new details of the case, which received national attention when police launched an expansive three-day manhunt for the assailant in the red pickup truck.

After Desper surrendered early on July 2, authorities processed his Chevrolet Silverado, finding gunshot powder residue as well as rounds, a magazine, and a holster, Torres said. No bullet holes were found on the passenger side of the car and the window was not shattered, he said, which would not be consistent with an accidental discharge. Desper's Smith & Wesson .40-caliber semiautomatic handgun was found in his bedroom. A friend of Desper's previously told the Inquirer and Daily News that Desper regularly kept a gun in the truck's center console.

Roberson, a recent graduate of West Chester's Bayard Rustin High School, had been driving from a shopping trip in Exton to her family's West Chester home when she was killed. Authorities said she and Desper were jockeying for position at the merger, just before Route 202, when Desper fired the fatal shot.

McGarrigle argued that there was no evidence Desper even looked at Roberson before shooting. Gualtieri told police that Desper said "he didn't know she was a beautiful little girl until the next day when he saw it on the news," according to police documents read in court.

Torres said there was no sign that Roberson's car and Desper's ever made impact. Desper was driving recklessly, Torres said, and since she was in the right lane, Roberson had the right of way.