He was found guilty of rape as a jury did not believe he had been given consent by the victim.
The footballer argued that the woman replied "yes" when asked if he could join in with sex between her and his friend.
In court the woman said she could not remember what she had said in the hotel room.
In criminal law the fundamental principle is that the burden of proof is on the prosecution (the people bringing the case) while the standard of proof is that a jury is sure of someone's guilt (formally known as  'beyond a reasonable doubt').
The legal definition of rape is:
The definition of consent and the law surrounding consent:
A key point for the jury was whether the victim had capacity to make a choice.
The footballer argues the woman, who had been drinking, had the capacity to make a choice.
The prosecution successfully argued she did not.
The 26-year-old has been refused the right to appeal, but the Criminal Cases Review Commission is studying his case.
Their job is to look at whether there's been a miscarriage of justice and could refer the case back to court.
When he was sentenced to five years in prison the judge said: "The complainant was 19 years of age and was extremely intoxicated.
"CCTV footage shows, in my view, the extent of her intoxication when she stumbled into your friend.
"As the jury have found, she was in no condition to have sexual intercourse.
"When you arrived at the hotel, you must have realised that."
The victim has since been named and abused on Twitter and had to create a new identity.
Criminal law solicitor Julian Young has worked on many rape cases.
He told Newsbeat: "The main difficulty with allegations of sexual offences is that they tend to take place between two people [and] rarely with a witness present.
"The task of the jury is to assess the evidence with life experience and access the credibility of the witness.
"Even if they find that the complainant is credible the jury still has to be sure of the guilt of the defendant."
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The Ched Evans trial hinged on the issue of consent.