The second murder trial began Tuesday for Karen Read, who is accused of causing the death of her Boston police officer boyfriend but whose supporters contend is being framed for a murder she didn’t commit.

Prosecutors say Read backed her SUV into John O’Keefe after dropping him off at a party and returned hours later to find him dead. Defense attorneys say she was a victim of a conspiracy involving the police and they plan, as they did in the first trial, to offer evidence pointing to the real killer.

Nine men and nine women were chosen to serve as the 12 jurors and six alternates.

Read has been charged with second-degree murder, manslaughter and leaving the scene. A mistrial was declared last year after jurors said they were at an impasse. The second trial will look much like the first, with the same judge, many of the same witnesses and several of the prominent defense attorneys.

A rocky relationship comes under scrutiny

Read had worked as a financial analyst and a Bentley College adjunct professor before being charged in the death of O’Keefe, who was 46 when he died. The 16-year police veteran was found unresponsive outside the home of a fellow Boston police officer.

After a night out drinking, prosecutors say Read, who is 45, dropped O’Keefe at the house party just after midnight. As she made a three-point turn, prosecutors say, she struck O’Keefe before driving away. She returned hours later to find him in a snowbank.

As at the first trial, prosecutors will try to convince jurors that Read’s actions were intentional. They are expected to call witnesses who will describe how the couple’s relationship had begun to sour before O’Keefe’s death, including his brother and sister-in-law, who testified that Read told her the couple had argued in Aruba after she caught O’Keefe kissing another woman.

The defense blames a third party for O’Keefe’s death

The defense is expected to portray the investigation into O’Keefe’s death as shoddy and undermined by the close relationship investigators had with the police officers and other law enforcement agents who were at the house party.

Among the key witnesses they will call is former State Trooper Michael Proctor, who led the investigation but has since been fired after a disciplinary board found he sent sexist and crude texts about Read to his family and colleagues. He is also on the prosecution’s witness list.

Proctor’s testimony was a key moment during the first trial, when the defense suggested his texts about Read and the case showed he was biased and had singled her out early in the investigation, ignoring other potential suspects.

They also are expected to suggest Read was framed, saying O’Keefe was actually killed inside the home during a fight with another partygoer and then dragged outside. In the first trial, defense attorneys suggested investigators focused on Read because she was a “convenient outsider” who saved them from having to consider law enforcement officers as suspects.

Ahead of the second trial, the two sides sparred over whether Read’s lawyers will be allowed to argue that someone else killed O’Keefe. Judge Beverly Cannone ruled Monday that attorneys can’t mention potential third-party culprits in their opening statements but will be allowed to develop evidence against Brian Albert, a retired police officer who owned the Canton home, and his friend Brian Higgins. Lawyers cannot implicate Albert’s nephew, Colin Albert, the judge said.

A town-commissioned audit of the Canton Police Department released March 30 found several mistakes with the investigation but no evidence of a cover-up. It suggested that first responders should have photographed O’Keefe where he was found before he was moved and that all interviews of “critical witnesses” should have been done at the department after O’Keefe was taken to a hospital.

The defense’s double jeopardy argument fails

Soon after the mistrial, Read’s lawyers set out to get the main charges dropped.

They argued Judge Cannone declared a mistrial without polling the jurors to confirm their conclusions. Defense attorney Martin Weinberg said five jurors indicated after the trial that they were only deadlocked on the manslaughter count and had unanimously agreed that she wasn’t guilty of second-degree murder and leaving the scene, but that they hadn’t told the judge.

The defense said that because jurors had agreed Read wasn’t guilty of murder and leaving the scene, retrying her on those counts would amount to double jeopardy. But Cannone rejected that argument, as did the state’s highest court, a federal court judge, and an appeals court.

Prosecutors had urged Cannone to dismiss the double jeopardy claim, saying it amounted to “hearsay, conjecture and legally inappropriate reliance as to the substance of jury deliberations.” Assistant District Attorney Adam Lally argued that the jurors never indicated they had reached a verdict on any of the charges and that the defense had ample opportunity to object to the mistrial declaration.

A new prosecutor steps in

The second trial will likely look similar to the first. It will be held in the same courthouse before the same judge, and dozens of Read’s passionate supporters are again expected to rally outside. The charges, primary defense lawyers and many of the nearly 200 witnesses will also be the same.

The biggest difference will be the lead prosecutor, Hank Brennan. A former prosecutor and defense attorney who was brought in as a special prosecutor after the mistrial, Brennan has represented several prominent clients, including notorious Boston gangster James “Whitey” Bulger, and experts think he might be more forceful than Lally was in arguing the case.

What evidence will be offered?

Prosecutors are likely to rely on eyewitnesses from the scene in the early days of the trial, counting on testimony from police officers and firefighters who recalled Read making comments that implicated her in the killing.

They also are likely to introduce evidence of a broken taillight on Read’s SUV that prosecutors argue was damaged when she hit O’Keefe and possible DNA from O’Keefe found on her vehicle.

The defense’s goal is to raise doubts about the prosecution case and plant the seed that she was framed. They are expected to introduce evidence of a sloppy police investigation, including the failure to search the house and mistakes in the police log.

They also are expected to suggest that a hair found on the taillight was planted and the police investigation was marred by a conflict of interest.