A California appeals court has upheld the conviction of Brock Turner, the former Stanford University swimmer who was sentenced to six months in jail in 2016 for sexually assaulting an unconscious woman, despite his lawyer’s argument that there was insufficient evidence and that Mr. Turner had sought only “outercourse.”

Mr. Turner was appealing his 2016 conviction on charges of sexual assault of an unconscious person, sexual assault of an intoxicated person and sexual assault with intent to commit rape. The felonies stemmed from his assault of a 22-year-old woman after she had blacked out from drinking at a campus party in January 2015, when he was 19.

In March 2016, the news of Mr. Turner’s sentence of half a year in county jail and three years’ probation set off a national outcry and drew attention to sexual assaults on college campuses. He served three months in jail.

His lawyer, Eric Multhaup, filed a 172-page brief in December 2017 saying that Mr. Turner did not get a fair trial for several reasons, including insufficient evidence and the exclusion of character witnesses. The brief included about 60 pages on how intoxicated the victim was on Jan. 18, 2015, the night of the attack.