But Mr Forrest and his wife gave a much different version of events.
"After dinner finished, conversation took quite a bizarre turn," Mr Forrest said. "Trina was asking all sorts of sexual questions of both of us - completely inappropriate."
Then, he said, Ms McLachlan gave an impromptu demonstration of her "martial arts" skills. During the demonstration, he said, Ms McLauchlan "fell forward of me, very hard and face down."
Judge Glubb said: "While it is possible, even probable, there was a punch, I am simply not satisfied given the inconsistencies [between the stories] ... Even if I am sceptical of Miss Badalyan's motives, I am simply unsure."
The text messages were referred to during the trial but not presented as exhibits.
Screen shots of the texts were given to the Herald earlier this year by Ms McLachlan.
In the text exchange, which began after Ms McLachlan arrived at Auckland City Hospital by ambulance, Ms Badalyan wrote: "Hope you are ok. Can't find right words now to tell you, just let you know I am on your side, and I told the police everything what happened."
"I am so sorry he is really screwed up. I am thinking now how to get away from him. He will do the same thing with me again sooner or later. Or at the end me and Leo will stay with nothing. Get well soon."
Ms Badalyan expressed concern about her husband's use of the donated money. "I think about fund money, he is going to waste it all, is it possible with good lawyer to take it from him?"
Ms Badalyan gave birth to Leo on January 21 in Armenia, where disabled babies are often put in orphanages, and initially disowned the boy. Mr Forrest made global headlines in February with an appeal to move his son from Armenia. Ms McLachlan acted as spokeswoman for Mr Forrest after an online appeal raised more than $600,000 for the baby from 17,900 donors.
While the couple were separated, Mr Forrest set up the Go Fund Me site, hoping to raise $60,000 to allow him to dedicate a year to raising Leo as a fulltime solo father back in New Zealand. The Leo Forrest Trust was set up to handle the windfall.
In court Ms Badalyan said of her text messages to Ms McLachlan: "I wrote saying I supported her. At that point I thought Trina was right."
Sam Forrest's cousin John Forrest gave evidence about going to the house in response to a phone call from Mr Forrest, who told him "something terrible" had happened. John Forrest cried in court when recounting finding Ms McLachlan curled up on the couch sobbing.
After the police had left, he spoke to Ms Badalyan, he told the court.
"She volunteered to me that this had been happening to her and she said I needed to be careful." He said he took that to mean "arguments".
Constable Robert Law told the court Ms Badalyan was on a "partnership working visa" and that Sam Forrest was her sponsor.
He said without her husband's support she would have to leave the country or get a new visa.
