An Orleans Parish jury was poised to deliberate into the night Monday in the trial of a 20-year-old Harvey man accused of murdering Harry “Mike” Ainsworth, an Algiers Point man who was trying to halt a neighbor’s carjacking nearly three years ago as his two young sons looked on.

In an animated closing argument, defense attorney Lionel “Lon” Burns lambasted a police investigation led by a homicide detective who was heading up her first case as lead investigator. Burns told the jury of six men and six women that police planted Kendall Harrison’s DNA — the central evidence in a case with no clear eyewitness identification, no murder weapon and no confession from Harrison to police.

Earlier Monday, an expert testified that material swabbed from the steering wheel of Anita Hedgepeth’s car following the Jan. 25, 2012, carjacking attempt and shooting turned up a “trace” DNA match to Harrison.

Burns suggested that police, frustrated at failing to solve a high-profile case that shook the city, took a shortcut to Harrison, whose name had been raised in tips to police.

“I contend that the DNA of Kendall Harrison was placed in this case. Reach your own conclusion. Was it added to the car? Were the swabs tampered with?” Burns asked.

Burns was aiming to exploit an admission by NOPD Detective Tanisha Sykes that she had failed to adhere to NOPD policy by neglecting to get two witnesses to sign photo lineups in which they fingered a “filler” photo, failing to identify Harrison.

“That’s the problem with this case. Nobody can make a reliable identification,” Burns told the jury. “Being the detective she is, she was going to make something happen. She was going to make something out of nothing. The whole police force was watching her.”

Assistant District Attorneys Payal Patel and Alex Calenda laid out an array of evidence during six days of testimony in the case, including family members of Harrison’s who placed him three blocks from the scene within a half-hour of the killing in the 500 block of Vallette Street.

Harrison had told detectives he was in Harvey at the time and hadn’t been in Algiers Point for more than a week before Ainsworth, 44, was shot twice in the chest through the windshield of Hedgepeth’s Saturn Ion.

Hailed as a good Samaritan after his death, Ainsworth heard screams and ran from the bus stop where he’d dropped off his two boys, ages 9 and 10, at 7 a.m. He leaped onto the Saturn’s windshield and bashed it with his arms and fists before the carjacker fired a 9mm weapon through the windshield.

Early in the trial, Burns portrayed Ainsworth as an overzealous vigilante.

Patel described Burns’ defense as “hoopin’ and hollerin’ ” and the theory of planted DNA as “disingenuous, cheap and dirty.”

“I think you’ve seen their desperation and their last-minute grasping of their last hope,” she said. “What do you do in the face of irrefutable evidence? The defense team has decided to attack the Ainsworth family. They’re grasping at straws.”

Patel cited testimony about the careful transport of the DNA evidence to the State Police lab in Baton Rouge. For the jurors to believe that Sykes planted DNA evidence, Patel told them, “You’d also have to believe in time travel.”

Harrison’s father, Michael Willis, took the witness stand to vouch for his son, saying Harrison, who was 17 when Ainsworth was killed, never owned a gun.

That opened the door for prosecutors to show the jury a photo taken from Harrison’s cellphone that showed him carrying a gun that Calenda said likely was the murder weapon.

Prosecutors rebuffed Burns’ suggestion that Ainsworth, a member of a New Orleans police booster group, invited his own death.

“I’ll tell you right now, Mike Ainsworth is a hero. Mike Ainsworth gave his life to protect a person he didn’t even know,” Calenda told the jury. “But that’s not why we’re here.”

Harrison faces a life prison term if the jury finds him guilty of second-degree murder. He also is being tried on an armed robbery count in the carjacking.

Patel wrapped up her closing argument shortly after 8 p.m., and Criminal District Court Judge Darryl Derbigny began reading instructions to the jury.

Follow John Simerman on Twitter, @johnsimerman.