Ulster and Ireland rugby player Paddy Jackson would be the "last person in the world" to rape someone, his friend has told Belfast Crown Court.
Rory Harrison, 25, from Manse Road in Belfast is accused of perverting the course of justice and withholding information about the attack alleged to have happened after a night out in June 2016.
He was asked about a message hours later in which the complainant stated what happened had not been consensual.
Mr Harrison told the court: "My initial reaction was shock that something had happened she was not consenting to.
"The more I thought about it, I have known Patrick since I was eight or nine. He is the last person in the world to rape someone.
"I didn't believe it. I thought she had maybe done something and then regretted it."
Paddy Jackson, 26, from Oakleigh Park in Belfast, and Stuart Olding, 24, from Ardenlee Street in the city, deny raping the same woman at a house party in Mr Jackson's home during the early hours of 28 June, 2016.
Mr Jackson denies a further charge of sexual assault.
The court had taken the unusual step of sitting on a Saturday in a bid to make up time in the high-profile case.
Mr Harrison spent almost two hours being questioned by his defence barrister Gavan Duffy QC.
He dismissed the woman's message and did not inform Paddy Jackson of its content when they met for lunch the following day, the court was told.
When asked why, the defendant said: "Because I did not believe it.
"I did not want to worry him (Jackson) about something I had absolutely no faith was true."
Mr Harrison, who has a history degree from UCD, has been close friends with the accused for years.
He attended Methodist College in Belfast alongside Mr Jackson and met Mr Olding later through rugby.
Answering questions about his perception of Mr Jackson in social situations, he said: "He's exactly the same guy I knew at mini rugby when I was eight or nine as he is now despite all he has been through."
Mr Duffy asked: "Has he been changed by his success?"
"Not at all," Mr Harrison said.
Judge Smyth also told jurors to wait until all the evidence had been heard before making up their minds.
Mr Harrison was not part of WhatsApp groups called "Jacome" and "The Juicers" in which explicit messages were exchanged, the court heard.
However, he was in text and telephone communication with Blane McIlroy, 26, from Royal Lodge Road in Belfast, who is accused of exposing himself to the alleged victim.
Mr McIlroy denies the allegation.
Mr Harrison explained comments about "hilarious scenes" as referencing the presence of Northern Ireland footballers at Ollie’s nightclub where the men had been partying, in particular a photograph he posted on Facebook of himself with the player, Will Grigg.
"Everyone was singing 'Will Grigg's on fire' and some people were taking their tops off," he said.
It was not a reference to the hilarity of a rape or sexual assault, the court was told.
"Would you ever think that?" asked Mr Duffy.
Mr Harrison answered: "Absolutely not."
Meanwhile, another message in which Mr Harrison wrote "walked upstairs and there were more flutes than 12 July" was described as a joke because he had presumed there had been consensual sexual activity between Mr Jackson and the complainant as well as Mr Olding and a different woman from the party.
"It was an attempt at humour," Mr Harrison said.
Mr Duffy asked: "If you honestly believed that a rape had taken place at Mr Jackson's house would you have joked about it?"
"No, I would not," said Mr Harrison.
The court has previously heard how the four defendants met for lunch at a cafe on Belfast's Ormeau Road the day after the alleged attack.
Prosecutors have suggested it was there they concocted a story or cover-up.
Mr Harrison was present 20 or 25 minutes, but left because he had to collect the family dog from the groomers, the court heard.
He denied there had been any clandestine conversations.
Mr Harrison is the last of the four defendants to enter the witness box of courtroom number 12 at the Laganside court complex.
His father, a solicitor who does not specialise in criminal work, and mother, a nurse, have supported him throughout the trial, the court heard.
He accepted being "fairly drunk" on the night in question having consumed six cans of beer, four pints of Guinness, a few gin and tonics, four or five vodkas and lemonade and a few shots.
There were some memory gaps, he admitted.
However, he did remember the woman "staring" at Mr Jackson and saw her "follow" him upstairs, he said.
Mr Harrison believed the complainant had been upset when she left the party because she had been "rejected" by Mr Jackson.
Mr Duffy said: "It has been speculated by the Crown that you knew or believed that she had been the victim of rape at that time?"
Mr Harrison replied: "No, I did not."
He also denied attempting to cover up or "manage" the woman.
Meanwhile, it was as Mr Harrison, Mr Olding and Mr Jackson were having lunch on 30 June, 2016 - his birthday - when senior figures at Ulster Rugby contacted the two players telling them to go to the police station, the court heard.
"I was surprised," said Mr Harrison who said he went home and slept.
Indeed, he was still recovering from the excesses of partying when the police called to his house to take a witness statement.
"I was woken by my sister at about 3pm. She said the police are in the kitchen. They want to speak to you."
He said he was "shocked", tired and hungover but gave a statement over the course of the one-and-a-half hour police visit.
He did not contact a solicitor, answered all of the officers' questions and did not lie, Mr Harrison told the court.
Message exchanges between Mr Harrison and Mr McIlroy after the police visit were also detailed to the court.
Mr Harrison said: "I thought she had maybe gone up with Patrick and had been engaged in some sort of sexual activity, regretted it and now she was saying this."
Mr Duffy said: "Did you believe there had been a rape or sexual assault?"
"No," answered Mr Harrison.
He also explained a comment in which he told Mr McIlroy to "leave" his phone if going to the police.
"I was aware that that police seize phones. It is pretty inconvenient when you lose numbers and photographs," he said.
His defence lawyer asked: "Were you trying to impede an investigation or conceal anything?"
"No, I was not," Mr Harrison said.
In October 2016, Mr Harrison was questioned by the PSNI under caution on suspicion of perverting the course of justice.
He had voluntarily attended the PSNI station in Belfast, without a solicitor on the understanding he was going to clarify points in his witness statement, it emerged.
However, having contacted his father, a solicitor was subsequently sent to represent him.
Mr Harrison said he answered every police question to the best of his ability and did not attempt to cover anything up.
Mr Duffy said: "Have you done anything to pervert the course of justice?"
Mr Harrison answered: "No, I have not."
The barrister added: "Have you concealed any criminal activity?"
"No I have not," he answered.
The case has been adjourned until Monday.
Dismissing the jury of eight men and three women for the weekend, Judge Patricia Smyth repeated warnings not to discuss the case.
The judge said: "May I remind you in the strongest terms possible do not discuss anything to do with this trial or the fact that you are sitting on the jury with either family or friends.
"Please, please abide by this direction."