The victim’s sister, a key witness, has petitioned Governor John Kasich to use his clemency powers to free Patterson, who has always insisted that she is innocent

Tyra Patterson, the Ohio woman who has been fighting for 22 years to clear herself of a life sentence for murder, has received a major boost to her hopes of freedom after the key witness and surviving victim in the case told the Guardian that she is now convinced of the prisoner’s innocence.

Patterson has always insisted that she was an innocent bystander in the murder of Michelle Lai, a 15-year-old girl who was shot in the head in 1994 in Dayton, Ohio. Earlier this year, the Guardian profiled Patterson’s struggle for justice in a three-part investigation that explored the profound inconsistencies in the prosecution case against her, her claim that she was forced to make a false confession, and the mounting campaign to have her released.

The injustice system: one woman's journey to prove her innocence – and be set free after 21 years Read more

Now, Holly Lai Holbrook, Michelle’s sister who was sitting in the car just feet from her when the teenager was shot at point-blank range, has come forward to say that on the night of the murder she told police officers at the crime scene that Patterson was not involved in the attack and had nothing to do with her sister’s killing.

“I remember pointing someone out that night and saying to the police: ‘She didn’t do it, she didn’t have anything to do with it’; that kept going around my head over and over again,” Lai Holbrook told the Guardian.

Though she did not know at the time the identity of the bystander that she pointed out to police in the early hours of 20 September 1994, Lai Holbrook clearly recalled how she looked, describing an individual who closely resembles the then 19-year-old Patterson. “She was biracial, dark, long hair. I recall she had a coat on, a fluffy coat.”

Facebook Twitter Pinterest Patterson has been fighting for 22 years to clear herself of a life sentence in the murder of Michelle Lai, a 15-year-old girl killed in 1994. Photograph: The Guardian/Courtesy of the Family

She added: “I remember the fact that there was somebody there who I didn’t think did anything. I remember pointing her out to the police.”

The new evidence comes at a crucial point in Patterson’s long struggle to clear her name. The prisoner, now 41, has petitioned the governor of Ohio, John Kasich, pleading that he use his powers of clemency and set her free.

A decision from the governor could come any day.

Patterson’s story embodies many of the flaws and pitfalls within the US criminal justice system that have seen the prison population rise to its current 2.2 million, almost a quarter of the total number of incarcerated people on the globe. Of those, more than 100,000 are women.

Facebook Twitter Pinterest Tyra Patterson’s story embodies many of the flaws and pitfalls within the US criminal justice system. Photograph: Laurence Mathieu-Leger/The Guardian

A Guardian investigation uncovered several glaring problems with Patterson’s prosecution. She was put under pressure by detectives on the day of the murder to say that she had grabbed a necklace from the neck of one of Patterson’s friends, Candice Brogan – a false admission, she insists, that made her vulnerable to a murder charge as an accomplice in Michelle’s killing.

Patterson was inadequately represented at trial, with her defense attorney at the time telling the Guardian that his handling of the case was in his view the lowest point of his career as a lawyer. The defense team dissuaded Patterson from going into the witness box because she “spoke too hood” – the prisoner is African American.

The trial defense team also decided to withhold from the jury a tape recording of a 911 call Patterson made to emergency workers soon after the murder happened. Six of the 12 members of the jury have given affidavits saying that if they had known about the 911 call they would have found her not guilty.

One juror told the Guardian that she had felt strongly that Patterson was innocent during the jury deliberation process but had caved in and gone along with the guilty verdict after it was pointed out to her that it was late and that a fellow juror was pregnant and needed to go home.

Lai Holbrook was 18 at the time of her sister’s death. She said she has spent many years wrestling with profound doubts about Patterson’s conviction but had buried those thoughts in part because she didn’t want to cause a row within her own family.

“I buried this stuff years ago. I knew I was wrong. But I didn’t want to be the black sheep of the family, the odd one out, and I didn’t want to have to relive that night, I just wanted it buried.”

She said that she had been encouraged by police officers and prosecutors to provide testimony against Patterson that would prove vital to her conviction and ensuing sentencing to life in prison. “When the police offered us little hints and pieces of information, it made it easier for me to overlook what really happened that night. The prosecutors were intimidating. Not just to me, to all of us. They were just scary. It seemed like they pushed the fact that all these girls did what they did, and that there was a confession.”

The prosecution never accused Patterson of direct involvement in the murder. Instead, it accused her of being an accomplice by arguing before the jury that she was part of a gang that attacked Michelle, her sister and two other girls in their car, robbed them of jewelry, physically assaulted them and then were complicit when the shooter, LaShawna Keeney, who is also serving a life sentence, pulled the trigger.

The prosecutors were intimidating … They pushed that all these girls did what they did and that there was a confession Holly Lai Holbrook

Central to the state’s case that Patterson was an active participant in the attack was that she snatched a necklace from one of the girls during the assault. But Patterson has always contested that her confession to doing so was forced out of her by detectives, and that in truth she only picked up the necklace from the ground as she was walking away from the scene of the assault in which she played no part.

The question of that necklace became a vital part of Lai Holbrook’s testimony, which was the core of the prosecution argument at Patterson’s trial. The state told the jury that the defendant, along with a 14-year-old girl called Kellie Johnson, had both been grabbing at a necklace worn by Brogan, who was sitting in the back of the car behind the Lai sisters.

Facebook Twitter Pinterest Jeannie Patterson praised the courage of Holly Lai Holbrook in making her statement: ‘What this young woman is doing is giving my daughter’s life back to her, and that is a great gift.’ Photograph: The Guardian/Courtesy of the Family

But Lai Holbrook’s testimony was inconsistent. In the earlier trial of Kellie, she told that jury that it had been Kellie exclusively who had grabbed at the jewelry, implying that Patterson had nothing to do with it.

Lai Holbrook – as she is now called, using her married name – told the Guardian that the idea that Patterson grabbed the necklace had been fed to her by detectives who said that Patterson had confessed to doing so, a confession that she insists was forced out of her. “Hearing about the confession made it easier on me,” said Lai Holbrook, 40. “I just wanted everyone that were involved to go to jail and stay there for the rest of their lives. Everyone who was there needs to pay. [The police] told us she had stolen the necklace, and when I heard that I was very, very angry – that made it easier to put her in jail too.”

The injustice system: Tyra Patterson proclaims her innocence. Is it time for her to come home? Read more

Lai Holbrook said that the attack on her, her sister, her cousin and a friend that night “was the scariest, most evilest thing I’ve ever had to deal with in my entire life. It was so scary, so horrifying, the way they treated us, the rocking of the car, the noises, the yelling, the nasty things they said to us. Them shooting my sister in front of me was just sickening. It was horrifying.”

She said the trauma of the events lived with her still, and over the years she has wrestled with mental stress and depression, and she remains on medication to this day. Part of the decision to come forward and talk about her true recollections of that night, and Patterson’s innocence, was that she had realized that she could not fully heal herself without doing so.

“Setting her free [means] I’m not tied down by all these chains of regret. I don’t have to hide any more. I don’t have to lie. She doesn’t deserve to be in jail, and I put her there. Her getting released would release me. I could finally say I did something right with my life.”

She doesn’t deserve to be in jail, and I put her there. Her getting released would release me Holly Lai Holbrook

The first person Lai Holbrook approached after she decided to speak out was David Singleton, executive director of the Ohio Justice & Policy Center, who has acted as Patterson’s attorney for the past four years. She asked to see the lawyer, whom she had never met before, at her sister’s grave on 16 March – Michelle’s birthday.

Singleton said that he was greatly moved by that graveside conversation. “I have never had a moment like that in the 25 years of my legal practice, where I am sitting with a victim who has had the courage to come forward as Holly Lai Holbrook did, knowing that she could be the key to setting free my client. And this was the victim whose sister was murdered right next to her – that makes this a very special case.”

The next step Lai Holbrook took was to write a letter to Kasich, the governor, setting out her clear recollections of what happened on the night of her sister’s murder. In the letter she described herself as a mother of four children and a “Christian woman who believes deeply in God and what Jesus teaches about forgiveness”.

She went on: “I feel bad that Tyra has been in prison so long for crimes I now believe she did not commit. I want to focus on what I can do to help obtain Tyra’s freedom and right the wrong she has suffered. That’s why I’m writing this letter.”

Kasich, who ran in this year’s presidential primaries as a moderate Republican alternative to Donald Trump, has not yet replied to the letter.

A few months ago, Patterson was transferred from the women’s prison in Dayton to an institution in Cleveland that prepares custodial inmates for possible life back in society following release. However, criminal justice experts in Ohio point out that residence in that prison is no guarantee of actual release.

Patterson’s mother, Jeannie Patterson, praised the courage of Lai Holbrook in making her statement. “I never thought this would happen. What this young woman is doing is giving my daughter’s life back to her, and that is a great gift.”