A man who was catastrophically injured after he jumped from a moving vehicle has sued the driver — his wife — for negligence, claiming she failed to apply the brakes after seeing he was about to jump.

Brian Lim took his case to the NSW District Court and, in a hearing in November last year, claimed his injuries would not have been as severe had Eunkyung Cho slammed her foot on the brakes of their Mercedes Benz.

The court heard Mr Lim and Ms Cho and their two children, aged four and two, had been out to dinner at a barbecue restaurant in Belmore in December 2012 when they began to argue after Mr Lim spoke with an acquaintance.

The argument continued on the drive home, when Ms Cho made a disparaging remark about Mr Lim's parents and he told her he wanted a divorce.

As the car travelled along Barker Road in Strathfield, Mr Lim opened the passenger door and Ms Cho reached across to grab him, before he jumped.

Police and ambulance attended the scene and the court heard Mr Lim was left with "catastrophic" injuries and was "under legal incapacity".

After hearing evidence from engineering experts with expertise in the biomechanics of traffic accident trauma, Judge David Wilson found that Ms Cho had been driving at about 50 kilometres an hour at the time of the incident, and that emergency braking could have caused injury to her "two very young children in the car" and to other road users.

The judge found that while Ms Cho had a duty of care to ensure Mr Lim's safety while in the car, that duty did not extend to protecting him from harm he caused to himself which he described as "entirely out of character".

"The vehicle was, at the time the incident occurred, close to home," Judge Wilson said, adding that a "reasonable person" would not have jumped from a car travelling at that speed.

"If the plaintiff wished to remove himself from the vehicle then a reasonable person in the position of the plaintiff would have waited until they arrived home before doing so."

He said that if Ms Cho had applied the brakes, there was no reason to believe that Mr Lim's injuries would have been less severe.

He also found that Mr Lim was guilty of contributory negligence and that any damages owed to him would be reduced "by 100 per cent".

Mr Lim appealed the decision in the NSW Court of Appeal, however it agreed unanimously with the District Court judge's ruling.

In a judgement handed down on Monday, Acting Justice Ronald Sackville said the case was "both unusual and tragic".

"There was no evidence … that [she] had any inkling prior to [him] opening the door of the vehicle that he would do something as dangerous as leaping from a moving vehicle," he said.

"Not surprisingly, at first she did not grasp that [he] would act as recklessly as he did.

"[Her] actions in a sudden crisis not of her own making were not unreasonable in the circumstances she faced."