The trial for the murder of a Northwestern University doctoral student began Monday with three witnesses reluctant to shed any light on what led to the 2018 shooting in Rogers Park.One of the witnesses, Elwin Pollard, took the stand wearing tan jail clothes because he was locked up for contempt of court after prosecutors claimed he ignored a subpoena to testify in the trial of Diante Speed, charged with the murder of Shane Colombo, 25.Pollard had told detectives in 2018 that he heard gunshots and saw two men running after another man. Stray gunfire from that attack killed Colombo as he walked home from a store near his newly purchased condo the night of Sept. 2, according to prosecutors.“I was only concerned with the gunshots,” said Pollard, who said he ducked down in his minivan when he heard shots and saw muzzle flashes. “I don't know if they were chasing him, or he was the one with the gun.”Prosecutors say Speed opened fire on a man who had taunted him and his friends as they walked down North Clark Street near Howard, just a block from the condo Colombo and his fiancé had purchased a few weeks earlier.The couple were looking forward to living together while Colombo was studying for his PhD at Northwestern, a program he had started the week he was killed.Just two hours before the shooting, Colombo had been on a video call with his fiancé, Vicente Colores-Chalmers, who was the first witness called by prosecutors Monday.When Colombo didn’t respond to text messages later that night, Colores-Chalmers used a phone app to find Colombo’s location: a hospital.“I called the hospital and was told immediately that he had passed away,” Colores-Chalmers said. As she sat in the courtroom gallery, Colombo’s mother’s face looked pained.Whether the man Speed was chasing was armed seemed to be a key point for Speed’s attorneys, who said in their opening statement that Speed can’t be guilty of first-degree murder because he was shooting at a man who had drawn a gun on him.The two other witnesses called Monday, both friends of Speed who had been with him the night of the shooting, were even less cooperative with prosecutors.Juwan Garrett declined to point out Speed in the courtroom when asked to identify his childhood friend, and had to be told by the judge to even describe what Speed was wearing in court.The other witness, Charles Moore, sparred with Assistant State’s Attorney James Papa for about 90 minutes, stating that he couldn’t recall answers he gave to a grand jury in 2019.Papa pointed out that Moore had said the man being chased didn’t have a gun, and that he had talked to detectives because he was troubled by Colombo’s death.Moore was more forthcoming when Speed’s lawyer, Assistant Public Defender Sarah Frensene, pointed out that Moore had told detectives, if not the grand jury, that the man they’d been chasing had a gun.“Is it your testimony today… that you saw the boy shooting in your direction?” Frensene asked.“Yes,” Moore said.The trial is expected to continue through Thursday.