Ian Bailey's partner, Jules Thomas, has told the High Court his violence towards her was "still a bad memory and kind of unforgivable".
However, Ms Thomas said she had eventually forgiven him because he was remorseful and she believed there was "good in everyone".
Ms Thomas was giving evidence for a second day in Mr Bailey's case for wrongful arrest.
She was questioned about three assaults on her by Mr Bailey in 1993, 1996 and 2001.
Ms Thomas described feeling disgusted and appalled after the assaults and said drink was involved, but that was never an excuse for violence.
She said a friend of hers called gardaí after the assault in 2001, but she did not ask her to do so.
Ms Thomas said she had been assured that Mr Bailey would not be arrested for that assault.
Instead, she had decided it would be best for him to stay with family in England for a while so she would not have to see him around, but when he went to the airport there was "a big arrest" with a media presence.
She said before this she had been getting visits from two gardaí who saw the assault as "an excuse to get me to say that Ian had committed the murder".
Mr Bailey, 57, from the Prairie, Schull in west Cork, is suing the Garda Commissioner, Minister for Justice and the Attorney General for damages for wrongful arrest in relation to his treatment as a suspect for the murder of Sophie Toscan Du Plantier in west Cork in December 1996.
The State denies the claims.
Ms Thomas broke down in the witness box as she described her arrest in February 1997 for the murder of Sophie Toscan du Plantier.
She said her arrest came as a complete shock and was like being hit with a plank.
In emotional testimony, she said: "I was in a terrible state of shock. It's very hard to describe the level of shock when you have nothing to do with anything like this."
She said from the beginning of her questioning gardaí "laid straight into me", saying Mr Bailey had done it.
Ms Thomas said: "They went on and on and on. There was no way they were going to believe he had not done anything."
She said she felt persecuted and felt there was something very wrong with what was going on.
Ms Thomas said: "I knew it was a stitch-up and I said that in the car and they got really irate with me.
"They kept telling me you will go down with him if you don't confess."
She also said gardaí told her Mr Bailey had confessed to the murder when in fact he never had. "I knew it wasn't true," she told the court.
Ms Thomas said gardaí were banging their fists on the table and shouting and she was intimidated and frightened.
She said Detective Garda Jim Fitzgerald was one of the worst, as he seemed very, very angry with her. "It was horrific," she said.
Ms Thomas said she believed when she was speaking that they were writing what she was saying, but when the statements were read to her she signed them without reading them. However, she later had a difficulty with them.
There were additions, omissions and inventions in the statements, she said.
Ms Thomas told the court she received a late-night phone call from a garda telling her to leave her home.
She said she asked the caller who it was and was told: "You know bloody well who it is."
The caller, who she says she recognised as Det Gda Fitzgerald, repeatedly told her to "Get the f*** out, get the f*** out".
She said it was very frightening to be told by one of the detectives to get out of her own home.
Ms Thomas said: "When you are being attacked by the forces of the law it is a very frightening experience."
She and Mr Bailey wrote a letter of complaint to the Minister for Justice, but were told to go to the Garda Complaints Board.
She said they did not do this as they had no faith in that system at the time.
Ms Thomas again broke down in tears as she was questioned about a second arrest and said: "I get so traumatised by these events because I know it was all so wrong."
She said she was put in an upstairs room and was not allowed to leave while the house was searched and left in a mess by gardaí.
Ms Thomas said she was in bed when gardaí arrived and was made to dress in front of a stranger, who also stood over her as she used the toilet.
She said the garda was running over her past relationships and told her they were useless.
Ms Thomas said they kept putting the same proposition to her over and over, that Mr Bailey had committed the murder.
She was later horrified to discover that her daughter Frenella, who was aged 16 or 17 at the time, had been arrested.
Ms Thomas said during her second arrest she found it very frightening when "you are not being believed by the people who are supposed to uphold the law".
During cross-examination, Ms Thomas was asked if she accepted there was a basis for entertaining suspicion that Mr Bailey might have had something to do with the crime because he was someone in the area guilty of serious violence against a woman.
She said there had been a few incidents in the area of "alcoholic violence" towards wives and it was not considered on the same level as murder.
Counsel for the State, Paul O'Higgins, asked if she accepted that if a big man was capable of significant violence against a woman and it was known, that is a basis on which the suspicion of gardaí might go more in his direction rather than an average person.
She replied: "Possibly, but finding a motive would be much more of a line to go on."
She was asked if she accepted that this together with statements from witnesses that Mr Bailey had admitted the killing would give the gardaí reasonable grounds to suspect him.
Ms Thomas replied: "I don’t know, possibly.”
She was asked if she accepted that information continued to come to gardaí after the first arrests.
She also said she did not trust the gardaí who were dealing with the case and did not trust the way they dealt with witnesses. "I know they are lying," she said.
It was also put to her that although she was arrested for the murder of Ms Toscan Du Plantier, it was made clear to her at all times that she was not directly suspected of murder but suspected of covering for Mr Bailey.
Ms Thomas said this was never made clear to her. She agreed she had been read her rights and told of her right to contact a solicitor.
Earlier, it was put to her that gardaí had good reason to investigate some of the anomalies made in answers to questionnaires in the days after the murder.
She agreed she had made mistakes when describing her movements on certain dates, but said these were later corrected.
