He took the witness stand on day 13 of his trial in the High Court at Christchurch, after the Crown closed its case at 10.54am, following evidence from the last of more than 100 witnesses.
Reid, 36, told of drug taking and rough sex with his partner, but he denies that he was the person who raped and murdered Christchurch woman Emma Agnew, or that he was the sex attacker who raped, sexually violated, robbed and attempted to murder a woman in Dunedin nine days later.
His ex-partner, who has name suppression, has alleged he admitted being involved, and Reid's evidence today targeted her credibility.
Defence counsel Glenn Henderson said the defence would call four witnesses, including Reid who then told the court of his relationship with his ex-partner.
He said he had lost count of the number of times she had dumped him.
The woman had claimed the relationship was "based upon sex" and Reid acknowledged that sex was a very big part of it.
"But it was a lot more complex than that because (the woman) and myself strove for the mental connection that goes along with the type of sex we have."
He disputed her portrayal that the sex was abnormal all the time.
"It was very normal on some days, and very abnormal on others depending on what mood took us at the time."
When main defence counsel David Bunce asked him about the woman's "sexual requirements", Reid took a deep breath.
"She liked the thought of being raped and controlled. She liked being tied up and strangled. She liked being cut, or hit, or degraded. She liked forceful rough sex."
Mr Bunce asked: "If she did not get these things, what would be the outcome?"
Reid replied: "To put it mildly, you would lose your job."
He told of the woman leaving her family to join him in Otago, and said that she took a lot of cannabis and some BZP party pills with her, and acted as a drug dealer in the area.
He said on one visit, they had "smoked copious amounts of pot and had copious amounts of sex".
On another visit, she bought a lot of cannabis leaf - known as cabbage - and they baked a large cake with it.
He told how the couple had a safe word for when the sex became too rough and one of them wanted to stop.
The ex-partner had chosen the word "rape" but Reid said he would have preferred the word "mercy".
"For me, mentally, it was in context."
He told of spending time in a mental hospital near Dunedin and then being driven back to Christchurch by the woman.
He spoke of having sex with the woman with the car parked near in Linwood, but denied that he had punched her in the vagina as she claimed in evidence.
Reid said he had never punched her in the vagina at any time.
The Crown case has included evidence of a similar injury on Miss Agnew, and the woman in Dunedin being attacked in the same way.
