The tragedy shook not only the community and those who knew Miss Pearn but the entire framework of the state's legal system.

The driver in the wrong lane on that night in March 2013 was the state's Director of Public Prosecutions, Tim Ellis, SC, a highly recognised and respected member of the legal community with a reputation for being a fierce cross-examiner.

In unique circumstances, the ruddy-faced man known for rigorously enforcing the state's law found himself as the defendant.

Amid concerns that a fair trial could not be conducted in Tasmania, two Hobart magistrates stood themselves down from hearing the case, and a Crown prosecutor was brought in from NSW to take on the Crown's case against Mr Ellis.

Mr Ellis was suspended on full pay when he pleaded not guilty to the charge of causing death by negligent driving. It is a position for which he receives $500,000 a year.

As Mr Ellis awaited trial, his understudy Darryl Coates, SC, was only able to step into the role of acting Director of Public Prosecutions after the laws were changed.

Mr Ellis arrived at the court each day on crutches with his wife, Anita Smith.

The pair, along with Miss Pearn's family, endured five days of television cameras camped outside the court, a reminder that the whole state was watching.

Former police commissioner Jack Johnston attended Mr Ellis's first appearance and day one of the hearing, smiling at journalists from the front row of the public gallery.

Mr Johnston was unsuccessfully charged with disclosing state secrets, a case which Mr Ellis tried to take to the High Court, and the relationship between the two was described as "frosty".

Miss Pearn's sister, aunt and uncle and cousins sat quietly in the hearing throughout the week, as intricate legal arguments were debated and Mr Ellis argued from the witness stand over the meaning of "tired and tired-er" and "sleepy and sleepier".

In the most dramatic day of the trial, Mr Ellis took the stand on Thursday.

Magistrate Chris Webster pulled him up several times to remind him that he was the one being cross- examined, and was not the prosecutor in this case.

"You are a defendant, Mr Ellis, not counsel," Mr Webster warned him.

Law students packed the public gallery, frantically taking down notes on a case that will no doubt be closely analysed in future classes.

When the closing arguments were handed down yesterday, Mr Webster said he would need to have "a very good look at the case".

The decision was pushed back until June 25 due to the complexity of the case and because Mr Webster and Mr Ellis have holidays planned.

What happened:

On March 24 last year, Natalia Pearn was driving home to Launceston from Hobart in her white Toyota Corolla. She texted her parents as she left to say she would see them soon.

As she moved into an overtaking lane on the Midland Highway near Oatlands to pass a Commodore towing a trailer, she was met head-on by a blue Mercedes that was travelling south in a northern overtaking lane.

Miss Pearn died instantly. The Mercedes then hit the Commodore and spun into a bank.

Mr Ellis was cut out of the Mercedes and suffered severe leg injuries, and Ms Smith, who was in the passenger seat, broke her collarbone and ribs.

Two days after the crash, Mr Ellis told police that he had no recollection of driving in the wrong lane, and it was possible he had fallen asleep or had been confused about the road markings.

Mr Ellis wrote to the parents of Miss Pearn to tell them there would not be an argument about her driving.

Five months later, Mr Ellis was charged with causing the death of a person by negligent driving and pleaded not guilty in the Hobart Magistrates court in October.

The prosecution case:

Crown prosecutor John Pickering, SC, alleged that Mr Ellis was driving in the wrong lane for up to one kilometre, or 26 seconds, before he collided with Miss Pearn, and his act of driving was "conscious and voluntary".

For Mr Ellis to be found guilty of causing death by negligent driving, Mr Pickering had to prove that Mr Ellis was conscious when he collided with Miss Pearn.

•Mr Ellis had been treated successfully for sleep apnoea and he was at no more risk of causing an accident than someone who did not have the condition.

•Mr Ellis told police he had "a good night's sleep" the night before the accident.

•He had not had an "onerous day" and had not drunk any alcohol or taken any drugs.

•He had rested between the drives to and from Launceston.

•He did not tell police he was tired, and Ms Smith had not observed Mr Ellis being tired in the car.

•It is "inconceivable" a vehicle could "deliberately" pull out into a centre overtaking lane and stay there without being conscious.

•The car was seen to be in control while driving in the wrong lane by three witnesses.

•A sleep expert said it was not possible to steer a car and be asleep.

The defence case:

Defence lawyer Michael O'Farrell, SC, said the prosecution's allegations were "extraordinary" and Mr Pickering could not win on the issue of "voluntariness".

•There was no evidence of Mr Ellis braking or taking evasive action to avoid the collision, which, if conscious, he would have done.

•Mr Ellis could have been half asleep, which would not be considered "conscious".

•A sleep expert said it was "plausible" that Mr Ellis could steer with "minor adjustments" while half asleep.

•Mr Ellis was 58 and had driven more than four hours in a day.

•It wasn't an "easy and relaxing" day because the Midland Highway required attention.

•Two witnesses should be treated "cautiously" because they were "confused as to what happened"

The reconstruction:

Crash investigators from Tasmania Police made seven video reconstructions of the alleged driving by Mr Ellis.

Senior constable Kelly Cordwell drove a Mercedes the same as Mr Ellis's on the stretch of road leading up to the accident where the car was first seen in the wrong lane.

Senior Constable Cordwell took her hands off the wheel to observe what the car would do. Each time the car veered back towards the left-hand lane, correcting itself.

Senior Constable Cordwell told the court on Monday that steering was required for the car to stay in the wrong lane.

When Mr Ellis took the stand on Thursday, he told the court he drove back to the scene of the accident in December, despite serious injuries, and was convinced he could have navigated the sweeping corner while asleep.