Lawyers for Brock Turner, the Stanford swimmer whose six-month sentence for sexual assault ignited a national firestorm in 2016, have testified in an appeal of the 22-year-old's conviction, saying Mr Turner only wanted to have “outercourse” with his unconscious victim.

Mr Turner was convicted of three counts of felony sexual assault after Swedish exchange students discovered him “aggressively thrusting” on top of a half-dressed, intoxicated woman outside a Stanford fraternity party in 2015. He was released from jail after serving just three months.

But Attorney Eric Multhaup told a California appeals court in San Jose on Tuesday that Mr Turner’s conviction should be overturned due to lack of evidence.

Mr Multhaup told the panel that Mr Turner had only wanted to engage in “sexual outercourse” with the victim, known as Emily Doe. The attorney defined “outercourse” as a “version of safe sex” that does not involve vaginal sex, according to a local NBC affiliate.

The attorney noted that Mr Turner was not naked and his genitals were not exposed when he was found on top of his victim. Mr Turner has previously admitted to partially undressing and digitally penetrating the woman.

Brock Turner leaves prison

Mr Multhaup also called into question the woman’s level of intoxication, saying there was “no evidence at what point she went from being incapacitated from alcohol to loss of consciousness", according to CNN.

The three judges on the panel appeared unimpressed by Mr Multhaup's argument, according to the Associated Press.

“I absolutely don’t understand what you are talking about,” Justice Franklin Elia said, adding that the law “requires the jury verdict to be honoured”.

Assistant Attorney General Alisha Carlile, representing the state of California, said Mr Multhaup had presented a “far-fetched version of events”. She noted that bystanders “could tell from 30 feet away” that the victim was unconscious, citing trial testimony.

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Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy A man carries a sign during the "Wacky Walk" to show his solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford students Miriam Natvig (L) and Jemima Oslo (R) carried signs in solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Alizabeth McGowan wears a 1/3 sign on her mortarboard to show solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford students wear a 1/3 sign on their caps to show solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. The 1/3 represents a statistic that claims one in three students will experience a sexual assault by the time they graduate college. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy A plane flies over Stanford University with a banner reading "Protect Survivors. Not Rapists. #PerskyMustGo" during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Stanford students are protesting the universitys handling of rape cases alledging that the campus keeps secret the names of students found to be responsible for sexual assault and misconduct. / AFP / GABRIELLE LURIE (Photo credit should read GABRIELLE LURIE/AFP/Getty Images) Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Signs against protesting a rapist are seen during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Signs against protesting a rapist are seen during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy TOPSHOT - A plane flies over Stanford University with a banner reading "Protect Survivors. Not Rapists. #PerskyMustGo" during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Stanford students are protesting the universitys handling of rape cases alledging that the campus keeps secret the names of students found to be responsible for sexual assault and misconduct. / AFP / GABRIELLE LURIE (Photo credit should read GABRIELLE LURIE/AFP/Getty Images) Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Signs against protesting a rapist are seen during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Signs against protesting a rapist are seen during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy A plane flies over Stanford University with a banner reading "Protect Survivors. Not Rapists. #PerskyMustGo" during the commencement ceremony at Stanford University, in Palo Alto, California, on June 12, 2016. Stanford students are protesting the universitys handling of rape cases alledging that the campus keeps secret the names of students found to be responsible for sexual assault and misconduct. / AFP / GABRIELLE LURIE (Photo credit should read GABRIELLE LURIE/AFP/Getty Images) Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford student Paul Harrison (C) carries a sign in a show of solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford student Paul Harrison (C) carries a sign in a show of solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Stanford students are protesting the universitys handling of rape cases alledging that the campus keeps secret the names of students found to be responsible for sexual assault and misconduct. / AFP / GABRIELLE LURIE (Photo credit should read GABRIELLE LURIE/AFP/Getty Images) Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford student Paul Harrison (C) carries a sign in a show of solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford student Paul Harrison (C) carries a sign in a show of solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy A woman carries a sign in solidarity for a Stanford rape victim during graduation at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy A woman carries a sign in solidarity for a Stanford rape victim during graduation at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty Stanford University holds commencement amid sexual assault controversy Stanford students John Lancaster Finley(L) and Brandon Hill(C) carry signs during the "Wacky Walk" to show their solidarity for a Stanford rape victim during graduation ceremonies at Stanford University, in Palo Alto, California, on June 12, 2016. Gabrielle Lurie/AFP/Getty

Attorneys for Mr Turner filed the appeal in December of last year, in an attempt to revoke the requirement that he resister as a sex offender for life. The judges now have 90 days to respond to the appeal.

Mr Turner’s six-month conviction in 2016 sparked a massive backlash against Judge Aaron Persky, who many said had been too lenient on the then-19-year-old star athlete. The judge was voted off the bench by Santa Clara County residents in June, following a years-long activist campaign.

The trial also ignited a national debate on the treatment of sexual assault victims. Emily Doe’s emotional testimony was read aloud in court and shared widely online. Also widely circulated were comments by Mr Turner's father, who lamented the fact that his son’s future would be marred by “20 minutes of action out of his 20-plus years of life".