The first time Marvielle Smith met Devante Billy, on a teenage double date in October 2012, Billy shot her friend Valan May in the back of the head, she testified Thursday.

The two couples then took the bus to a black-dress theme party, leaving the 24-year-old UNO student and Navy veteran dying in the driver’s seat of his car. Four spent shell casings lay scattered across the front seats.

Smith and Billy went on to see each other romantically until his arrest in connection with the murder a few weeks later. After that they spoke by phone.

A photo posted on social media shows the pair lying close together, though Smith claimed Billy threatened her and that she feared for her life.

“He wasn’t going to leave my house if I don’t see him,” she testified.

Her troubling account, and a similar one from the other girl at the scene that night, Aalilyah Cobb, came as a weeklong trial for Charles “Mob Chuck” Carter at Orleans Parish Criminal District Court shifted from the Oct. 2, 2012, shooting that left Uptown lawyer Sanford Bull “Sandy” Kaynor Jr. paralyzed to May’s killing 17 days later.

Carter, then 16, was the other boy on the deadly night out, the two girls said.

Billy, 21, still awaits trial on his role in the armed robberies and shootings by alleged members of the “Marley Gang.”

Carter, 19, faces charges of second-degree murder, attempted murder, armed robbery and aggravated burglary for what authorities describe as an armed robbery spree turned deadly.

Prosecutors Jason Napoli and Alex Calenda rested the state’s case late Thursday after three days of disturbing testimony along with DNA and fingerprint evidence placing Carter at both shootings.

Smith testified that she and Cobb were hanging out with Billy and Carter when she called May to the 7900 block of Burke Avenue in New Orleans, seeking a ride on the night of Oct. 19, 2012.

When May arrived, she said, Carter strode up to the open driver’s window, pointed a gun at him and demanded money.

“After Valan told him he didn’t have no money, (Carter) said, ‘Gimme the (expleteive) money,’ and Valan gave him the wallet,” Smith testified.

Billy then approached the passenger side and grabbed May’s GPS navigation system, walked around the back of the car and got inside behind May, she said.

“You don’t know who y’all (messing) with,” May said, according to Smith.

“And Chuck said, ‘Just kill him.’ He gave Devante the gun and (Billy) started shooting.”

Smith said they all then hopped on a bus, headed for the party in black. Billy started bragging to another rider: “My dude said, ‘Get him,’ so I got him,” she told the jury.

Defense attorneys Gregory Carter and John Fuller pressed both Smith and Cobb, who were 16 and 15 at the time, on their initial statements to detectives, in which they denied any knowledge of May’s killing.

The attorneys also have suggested to the jury that May was there not to give a ride but to buy marijuana.

Cobb said she feared for her life and that of her family. She acknowledged that she never called 911 that night, despite describing May as like an older brother.

“Do you regret making that decision, not calling 911 that evening?” Napoli asked her.

“Yes, ’cause I coulda probably saved his life,” she replied. “I was scared. I didn’t know any better. I was 15.”

She said she dove into a bush after the gunfire, then caught up with the group at the corner, where Carter showed her the cellphone he’d stolen from the dying May. On the phone’s screen was a photo of May and Cobb together, she said.

Cobb said she didn’t see the shooting but saw Billy running afterward with the gun. She’d been standing behind the car on the phone, talking with Smith’s jailed boyfriend, Joshua “Joker” Domino, who was behind bars on gun charges.

Prosecutors played the jailhouse call, in which the jury heard Cobb fashioning an elaborate lie to cover for her friend before gunshots rang out.

The jury also heard two other jail calls late Thursday, with Charles Carter on the line while awaiting trial last year.

In one call, Carter lamented the 45-year prison sentence that an alleged cohort, Byron “Poodie Man” Johnson, accepted last year for his role in the armed robbery spree, including the attack that left Kaynor, then 58, paralyzed and mute.

“Forty-five?! Oh, serious? Dang,” Carter says in a call on Sept. 15, 2015, the day after Johnson’s plea. “I’m trying to take 10 or 15.”

Carter later says he’d accept a deal for 20 years “if they throw in the murder charge.”

At the end of a subsequent call with his girlfriend, Carter twice tells her, “Go make that money.”

Carter’s attorneys sought to discredit the testimony of the two female witnesses, citing their early lies to police and alleged threats by NOPD Detective Darrell Doucette that they would face murder charges and troubles in jail.

“I told her if she had anything to do with the murder she would go to jail,” Doucette testified Thursday. “That’s not a threat.”

A police fingerprint technician testified that a print matching Carter’s left ring finger was found on the driver’s door of May’s car.

Carter’s attorneys returned Doucette to the stand late Thursday before resting their case without calling Carter to the stand.

Closing arguments are expected to start Friday morning.

Follow John Simerman on Twitter, @johnsimerman.