A father’s defence of a former Stanford University student convicted of sexual assault has sparked outrage for referring to the crime as “20 minutes of action” that should not be punished with a prison sentence.

Brock Turner, 20, was sentenced last week to six months in county jail and three years' probation after he was convicted of sexually assaulting an unconscious woman on campus in January 2015.

The crime was interrupted by two graduate students who saw Turner assaulting a partially clothed woman behind a trash bin. Court heard that Turner tried to flee, but the students tackled and pinned him down until police arrived and arrested him.

The case made international headlines after the victim’s harrowing impact statement was published in full.

Now, a letter that Turner’s father, Dan Turner, wrote to the judge who presided over the trial, is making the rounds online.

In his defence of his son, Dan Turner wrote that the former Stanford swimmer should not have to pay a “steep price” for “20 minutes of action out of his 20 plus years of life.”

“What I know as his father is that incarceration is not the appropriate punishment for Brock,” the father wrote, adding that his son has never been violent, including on the night when the sexual assault took place.

In his letter, Dan Turner also wrote that his son will never be the same as a result of his conviction and no longer enjoys eating steaks or raiding the family’s chips and pretzel stash.

The letter appears to have been written before the judge handed down Brock Turner’s sentence, decried as incredibly lenient by the prosecutors and advocates for sexual assault victims.

The online reaction to Dan Turner’s letter was swift and visceral.

In a statement issued Monday, Stanford University said it “did everything within its power to ensure that justice was served in this case.”

The university said it facilitated an “immediate police investigation” before banning Turner from setting foot on campus.

“This is the harshest sanction that a university can impose on a student,” the university said.

“There has been a significant amount of misinformation circulating about Stanford’s role,” the statement said. “In this case, Stanford University, its students, its police and its staff members did everything they could.”

Stanford said it also “confidentially” reached out to the victim to “offer her support and tell her the steps we were taking.”