Despite having a condition that caused brittle bones the skull of journalist Phillip Cottrell seemed normal when a piece was removed during surgery, a jury has been told.

Cottrell died after being assaulted walking home in central Wellington from a night shift at Radio New Zealand almost a year ago.

Neurosurgeon Martin Hunn said emergency surgery was done to try to rescue the situation even though there were already signs that Cottrell had only an extremely small chance of survival.

Hunn was giving evidence in the High Court where Nicho Allan Waipuka, 20, and Manuel Renera Robinson, 18, are on trial charged with murdering Cottrell. They have pleaded not guilty.

In court he was shown two pairs of shoes and asked if a shoe could be consistent with causing that type of injury.

Hunn said the curved edges of the toe and heel of one pair with a relatively hard sole could have caused it if used with sufficient force.

The other pair of shoes had a softer sole and he was less certain about the toe of those shoes but the heel could have caused the injury, he said.

Hunn said the pattern of fractures to Cottrell’s skull was more extensive than what he usually saw, so his underlying brittle bones condition played a part in the extent to which the skull fractured but during surgery he had taken out part of the skull and the bone had seemed quite normal.

Significant force would have caused the degree of fracturing, Hunn said.

Hunn said on the front and left of Cottrell's head there were multiple small fractures and several fractures radiating outwards.

Although a small improvement was seen at first Cottrell's brain started to swell alarmingly and there was "torrential" bleeding.

He died the following day.

Hunn said Cottrell’s injuries reminded him of two cases where the cause of the injury had been known. One was caused by a vase and the other a hammer, both driven with great force.

Cottrell’s bone condition may have predisposed his brain to bleed more.

Yesterday the jury heard that two members of Robinson’s extended family had told police that Robinson had talked of kicking or stomping a man.

However in court one of the witnesses said he lied to police and the other said he was not sure what Robinson had said.

- © Fairfax NZ News