An English police officer in charge of crowd control at a 1989 soccer match at which 96 people were crushed to death was acquitted Thursday of gross negligence manslaughter, frustrating families of the victims who had campaigned for nearly three decades for officials to be held responsible for the tragedy.

Prosecutors alleged that David Duckenfield, now 75, bore "personal responsibility" for the deaths of 95 Liverpool fans at the Hillsborough stadium in Sheffield on April 15, 1989, during an FA Cup semifinal match against Nottingham Forest. Under British law, Duckenfield could not be charged in the death of the 96th victim, Tony Bland, who died more than a year and a day after suffering severe brain damage in the tragedy.

The Hillsborough tragedy remains Britain's worst sports disaster and led to the elimination of standing-room-only terraces at the country's largest soccer stadiums.

A crush of people at the Hillsborough stadium in Sheffield, England resulted in the deaths of 96 Liverpool fans on April 15, 1989. (AP Photo, File)

Gasps were heard from the public gallery at Preston Crown Court as the verdict was delivered at the climax of a trial that lasted six weeks. Duckenfield sat, impassive, in front of the dock with his hands clasped and then drank from a glass of water as the foreman of the jury delivered the verdict. One of the female jurors left the courtroom in tears as she and her colleagues filed out.

Christine Burke, whose father Henry died that day, stood in the public gallery and addressed the judge.

"With all due respect, my lord, 96 people were found unlawfully killed to a criminal standard," she said. "I would like to know who is responsible for my father's death because someone is."

Margaret Aspinall, the chair of the Hillsborough Family Support Group, echoed Burke's comments, calling the verdict “disgrace to this nation.”

"The question I'd like to ask all of you, and people within the system, is, 'Who put 96 people in their graves?” she told reporters after the verdict. “Who is accountable?"

The victims were originally ruled to have died accidentally, but that judgment was overturned in 2012 after documents uncovered mistakes by authorities and a cover-up by police, following a long campaign by families of the victims. Duckenfield stood trial earlier this year but the jury was discharged after failing to reach a verdict and a retrial was ordered.

Evidence presented in court showed Duckenfield ordered the opening of exit gates at the Leppings Lane end of the Hillsborough ground eight minutes before the game kicked off, after the area outside the turnstiles became dangerously overcrowded.

Floral tributes at Liverpool's Anfield stadium following the tragedy. (AP Photo/ Peter Kemp, File) (The Associated Press)

More than 2,000 fans entered through one of the exit gates once it was opened and many headed for the tunnel ahead of them, which led to the central pens where the crush happened.

The court was played audio of Duckenfield giving evidence to inquests in 2015. At the hearings, he accepted he should have taken steps to close the tunnel to the central pens after ordering the opening of the exit gate. Duckenfield did not give evidence in the trial because he was suffering from post-traumatic stress disorder.

Defense lawyer Benjamin Myers told the jury Duckenfield did “what he was expected to do as match commander.”

“He didn't breach his duty,” Myers said, “he did what he was expected to do in difficult circumstances."

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"David is, of course, relieved that the jury has found him not guilty," attorney Ian Lewis said on Duckenfield's behalf. "However his thoughts and sympathies remain with the families of those who lost their loved ones.”

Graham Mackrell, a former official of Sheffield Wednesday soccer club, stood trial with Duckenfield in January and was found guilty of failing to discharge his duties under the Health and Safety at Work Act. The club has played its home games at Hillsborough since 1989.

The Associated Press contributed to this report.