The trial of Thaddeus Ross in a 2011 shooting that left one person dead and four — including a 3-month-old girl — injured began Wednesday with sparring over the credibility of the prosecution’s star witness, a man who is himself accused of attempted murder in a separate case.

Ross, who faces a second-degree murder charge, was arrested in 2013 for his alleged role in what prosecutor Brittany Reed called the “Valentine’s Day Massacre.”

She argued in her opening statement that five people could have died on Feb. 14, 2011, when Ross and two accomplices allegedly participated in a drive-by shooting in the 800 block of Felicity Street.

Reed did not say what Ross’ motive was but called it a “senseless, violent act.”

Lewis “Lucci” Cook was taken to Interim LSU Hospital that day with multiple gunshot wounds. He later died. London Myers — a toddler at the time — was hit in the thigh by a bullet, and the wound still affects her today, Reed said.

Whether Ross, 24, is ultimately convicted in the shooting could depend in part on whether a jury of six men and six women buys the testimony of an alleged witness, Corey Jackson.

Jackson, 27, was questioned by New Orleans detectives immediately after the crime took place, but he did not connect Ross to the shooting at the time, said Ross’ defense attorney, Morris Reed Jr.

“Corey Jackson was shown a picture of my client on Feb. 17, 2011, and asked, ‘Do you recognize this person?’ ” Morris Reed Jr. said. “And Corey Jackson said, ‘I recognize him, but he had nothing to do with it.’ ”

Jackson did not identify Ross as the shooter until 2013, while he was incarcerated on a charge of being a felon in possession of a firearm. He was being debriefed by New Orleans Detective Richard Chambers, who also is expected to take the stand.

Jackson is now also scheduled to go on trial for attempted second-degree murder, and Morris Reed said that should call into question his reliability as a witness.

“Corey Jackson is a dishonest witness,” he said. “He’s a criminal. He’s facing life in prison, and he’s trying to tell the police what they want to hear to get a get-out-of-jail-free card.”

Brittany Reed, the prosecutor, rejected that charge, claiming that Jackson has always known that Ross was the shooter.

“Corey Jackson will tell you that he was able to make an identification of a person he always knew. Back in February of 2011 he knew it,” she said. “He was certain then. He is certain now that it was Thaddeus Ross who was the person who opened fire along with ‘Chicken’ on those individuals in that parking area.”

“Chicken” is Jamal Phillips, who, along with Ross and Tony “YaYo” Lacour, allegedly helped commit the drive-by shooting from a white Cadillac. Both Phillips and Lacour are dead, killed in December 2011 and June 2012, respectively.

Jackson will not be the only witness to testify, however. To the apparent surprise of the defense, the prosecution alluded to another witness who will take the stand: Paul Robinson.

Chambers, the detective, got Robinson’s name while investigating the shooting last year. Prosecutors say Robinson was approaching the group of victims when the shooting happened, and that he saw the shooter as he took cover.

“At the end of the day, you will learn that once Detective Chambers showed Mr. Robinson that photographic lineup, which included Thaddeus Ross, he was able to make a positive identification of Ross,” Brittany Reed said.

Ross’ attorney was unaware Robinson would be a witness.

“I’ve been coming to court for this case over a year,” Morris Reed Jr. said, “and I’ve never heard of anybody named Paul Robinson before.”

The trial is expected to last at least until Friday.

Follow Benjamin Oreskes on Twitter, @boreskes.