A police serious crash investigator's report into a fatal accident on the Ladies Mile highway near Queenstown last year was criticised by two peer reviewers, a court heard yesterday.

Prosecutor John Young and defence counsel Miles Beresford questioned Senior Constable Alastair Crosland about reservations expressed by two fellow serious crash unit investigators about his report on the accident, which claimed the life of Cromwell woman Jennifer Claire Scott (76).

Snr Const Crosland was giving evidence on the first day of the judge-alone trial of Auckland man Isac David Madsen (19) before Judge Mark Callaghan in the Queenstown District Court.

Madsen is charged with careless driving causing the death of Ms Scott on July 31 last year.


Mr Young asked Snr Const Crosland about the stance of Constable Glenn Marshall, of Wellington, who had refused to sign a report peer-review certificate on the grounds that vital measurements were not taken at the crash site and criticised aspects of its layout, grammar and brevity.

Snr Const Crosland said the information Const Marshall had believed was missing was concealed by a quirk of a software program, but was still contained in the report's data.

The report had been ''necessarily brief'' because it had been a preliminary report at that stage.

Another member of the serious crash unit, Senior Constable Chris Pelosi, had read the final report and found its calculation ''robust'' and its conclusions correct, Snr Const Crosland said.

Mr Beresford said Snr Const Pelosi had emailed Southern road policing manager Inspector Tania Baron to say he would only sign the certificate on the condition it was amended to state Snr Const Crosland's scene and vehicle examinations had ''not followed best practice''.

Snr Const Crosland said Snr Const Pelosi was not in a position to criticise the examinations because he had not taken part in them.

Asked why a signed report peer review certificate had not been produced in court, Snr Const Crosland said he understood it existed but did not know where it was.

His final report concluded the two vehicles had collided head-on while travelling at estimated speeds of 90kmh to 95kmh.

Madsen's car had been ''almost or completely across'' the centreline at the point of impact, while Ms Scott's car had remained within her lane.

He concluded Madsen was responsible for the crash because he had crossed the centreline, possibly as a result of fatigue or distraction.

Mr Beresford asked Snr Const Crosland if he was aware of a toxicology report that revealed the presence of a drug in Ms Scott's system, used to treat heart conditions, which had fatigue among its side effects.

Fatigue may have caused Ms Scott to move across the centreline before correcting, beginning a ''snaking'' effect.

Snr Const Crosland said he did not consider that information important because there was no evidence Ms Scott had crossed the centreline.

He rejected the assertion of the defence's crash expert, Tim Stevenson, that his report was ''seriously flawed''.

However, he accepted it was incomplete in some respects because it did not contain information such as witness statements or any photographs other than his own.

A witness to the crash, Arrowtown man Steve Murch, said he was driving towards Queenstown about 3.30pm when he noticed a car about 150m in front of him ''drift'' across the centreline.

It almost immediately collided with an oncoming car, and he saw both vehicles become airborne before crashing back to the road and skid.

A volunteer firefighter and St John officer, he called emergency services and took charge of the scene.

He saw an elderly lady motionless in one of the cars, face down in an inflated main airbag.

After climbing into the vehicle through a window, he found she was trapped, but sat her upright and checked her vital signs.

Her pulse was faint, then faded and stopped, Mr Murch said.

Under cross-examination by Mr Beresford, he said he did not recall telling Queenstown police officer Sergeant Keith Newell that he saw Madsen's vehicle ''weaving'' before the crash.

The term was ''not an apt description'' for what he witnessed, he said.

The trial resumes today.