Devin Baham tried to convince a St. Tammany Parish jury that he knew nothing about the stabbing death of 32-year-old Ashley King or the attempt to conceal the crime by pouring gasoline on her corpse and setting it ablaze.

But the jurors didn’t buy his testimony that he was left in the dark about the brutal murder or grisly cover-up in 2012 and that Andrew Sumner, a spoiled, rich boy who was as close as a brother to the defendant, acted alone.

After about four hours of deliberation, the jury returned three unanimous guilty verdicts late Friday night at the end of a weeklong trial: for manslaughter, aggravated arson and obstruction of justice.

While jurors weren’t convinced by Baham, they also showed skepticism that he had called all the shots, stabbing King 13 times and orchestrating the cleanup, as Sumner had testified in claiming he was a passive and reluctant sidekick.

Baham had been charged with second-degree murder, but the jury returned a lesser verdict of manslaughter, which carries a sentence of up to 40 years rather than life without hope of parole.

Baham ended up convicted of the same set of charges that Sumner pleaded guilty to in a March agreement with the 22nd Judicial District Attorney’s Office that required him to testify against Baham.

He will be sentenced by Judge Allison Penzato on June 22.

The verdict seems to line up with a version of King’s death in which the pair of friends acted in concert to rob the Slidell woman who sold Oxycontin to Sumner — and in which they were equally culpable in her death and the later arson that threatened the lives of others in the apartment building.

Prosecutors had sought in their closing arguments to hang the greater share of the guilt on Baham, calling Sumner a weak follower, a “beta male” who was trying to please his “alpha” friend.

But Assistant District Attorney Julie Knight told the jury that they could also decide that Baham should be found guilty of the same charges as Sumner, and that’s what happened.

The state had offered a similar deal to Baham on Monday, before the jury was empaneled. Martin Regan, Baham’s attorney, said the offer was to plead guilty to manslaughter as a first offense. But he said his client was adamant that he was not guilty and is “still adamant that he is not guilty’’ and so decided to go to trial.

The jury’s decision means that all three of those who were implicated in King’s death, including Katelyn Lusich, who drove the getaway car and assisted in the cover-up, will serve time in prison, but how much is unclear.

Sumner testified that he could serve as much as 100 years, although his plea agreement opened the door to a lesser sentence. He is slated for a status hearing June 24 to determine when he will be sentenced.

Lusich, who was 17 at the time of the crime and 7 1/2 months pregnant with Sumner’s child, pleaded guilty in September to obstruction of justice, which carries a sentence of as long as 40 years. But she’d be eligible for parole in 15 years. She has not yet pleaded to the charges of second-degree murder and aggravated arson, but those counts are expected to be dropped as part of her plea deal.

As for Baham, he will be multiple-billed because of prior theft convictions, according to Regan. However, his defense team plans to bring up several issues, including the fact that the aggravated arson charge against him was for burning down an apartment on Moonraker Drive — not Bayou Lane, where King lived and was killed, an error that Regan brought up in closing arguments.

The state produced no evidence that Baham torched an apartment on Moonraker, Regan said Saturday, and because of that, he expects the aggravated arson conviction to be dismissed. That also has implications for the obstruction of justice charge, he said, because it arguably hinges on the arson charge.

Regan said he was pleased that Baham was not found guilty of second-degree murder, but he plans to seek a new trial on the manslaughter charge.

Baham’s team had asked for a mistrial on the final day of the trial based on what Regan called prosecutorial error. Baham had exercised his right to remain silent when he was arrested, and he testified to that effect while on the stand. But even after he said he had invoked his constitutional right, the prosecution still asked Baham a number of questions about why he didn’t give police information.

Regan asked Penzato to instruct the jury to ignore that part of the cross-examination, but she declined. The defense then asked for a mistrial based on her refusal; Penzato again declined.

Regan said he expects that matter and others to get traction on appeal.

Follow Sara Pagones on Twitter, @spagonesadvocat.