A coroner says he’s disappointed a key witness failed to give evidence at the inquest into the death of Christchurch woman who fell from a moving car.

David Crerar has adjourned the hearing into the death of Libby McKay in June 2013.

Ms McKay was travelling home from a party with her boyfriend Mike Brown when he says she rolled out after an argument.

However Mr Brown refused his witness summons and could not be questioned further about what unfolded.

Earlier, a pathologist has told a coroner's hearing into the death of Libby McKay, the Christchurch woman most likely died from falling from a moving car. 

The 27-year-old and her partner Michael Brown were travelling home from a party in June 2013 when the accident occurred.

She died in hospital a few days later.

Pathologist Martin Sage told the hearing Ms McKay’s injuries was more likely to have being caused by falling from a moving vehicle, than from being hit by a car while standing outside the vehicle or being assaulted

He says McKay's injuries were largely internal, and it would have been unclear from looking at her just how bad the injuries were.

Meanwhile, there are conflicting statements from the boyfriend of a Christchurch woman who died after falling out of a car at high speed.

A friend of Mike Brown told the court, Brown told him the 27-year-old was asleep and simply stepped out of the moving car when he told her they were almost home.

However, ambulance officer Shona Tovey told the court when she first arrived on the scene Mike Brown admitted they were having an argument when the accident occurred.

And in a statement, a long time friend of the 27-year-old said Libby told her Brown had previously strangled her, and used her money on his mortgage.

The friend told police she doubted Ms McKay had stepped accidentally out of the car, but suspected she was either trying to get away from Brown or was pushed out by him.