The prosecution case is that Mr Scott deliberately ran over Ms Treacy following a long-running dispute over land. Mr Scott's lawyers have said her death was a tragic accident.

Garda Eoin O'Connor told prosecution counsel Dean Kelly SC today that on June 26, 2018, he carried out an analysis of the sight lines for a person of Mr Scott's height sitting in the cabin in a normal driving position. He said Ms Treacy was 1.62 metres (5'4") tall and his analysis established that the driver would have good visibility of an object 1.62 metres tall to the front, to the left and to the rear left.

At no point, he said, was the 1.62 metre tall object completely out of sight. The boom to the right, he said, did cause a significant reduction in visibility to that side.

Gda O'Connor told Mr Kelly that he is a forensic investigator with the road policing unit and has received training in collision investigation.

He arrived at Derryhiney about four hours after Ms Treacy had died and noted that it was a dry and clear evening and it hadn't been raining for some time. The following day he returned to map the yard where Ms Treacy's body and the teleporter were found.

The yard had a rough concrete surface typical of most farmyards, he said, and was on a slope of no more than 2 degrees. He noted a number of steel girders and water troughs which narrowed the available space between the various farm buildings.

The only obstacle-free path from Ms Treacy's back door to where her body was discovered covered a distance of 45 metres and went partly along a driveway to a calf shed and then through the yard between the troughs and girders.

He said the most likely point of impact between Ms Treacy and the teleporter was at the vehicle's back left wheel where bodily fluid and tissue were visible. It was not clear whether she was standing or walking when the impact happened or if she had fallen prior to impact.

Gda O'Connor drove the vehicle and found it was in a normal, front-steering mode and was in good working order. When he reversed, he noted that the audible alarm was working and told Mr Kelly that the purpose of the alarm is to warn people nearby.

He drove over a car tyre and some concrete blocks to see what impact the driver would feel from the cabin. He said this was not a rigorous test and is highly subjective but he noted that the movement was "not very significant".

The windows on the cabin had not been cleaned for some time and so visibility through those was reduced, he said. To the driver's left, above the door, there was no glass, allowing the driver "full visibility" in that direction.

The jury was shown a photograph of the view through the rear window from the cabin.

Gda O'Connor described the layout of the teleporter. The cabin is between the left front and rear wheels and the boom for the loader is to the right. The boom extends to three metres at the front and vertically to five metres above ground level. The boom and the loader would reduce visibility to the right, he said, and the engine would reduce visibility to the rear.

Gda O'Connor also placed a mannequin lying on the ground at different points to investigate the view if Ms Treacy had been lying down or had fallen in the yard. He said there were significant blind spots to the rear directly behind the engine for an object with little or no vertical height. He added: "However, to the left of the driver and on the rear on the left side there are no blind areas."

The trial has heard that in a voluntary interview with gardaí, Mr Scott said that when reversing the teleporter, he didn't know how fast he was going, that he only had a mirror on one side and it "wouldn't be great" because the boom would block his vision.

Normally, he said he would look over his right shoulder and thought his visibility was "okay". When he thought he hit a trailer, he said he pulled forward before getting down and finding Ms Treacy lying on the ground behind the teleporter. He said he called to her and thought he saw her moving her head and right arm.

An optometrist has also given evidence to the trial, telling the jury that after a June 2017 examination she noted Mr Scott had perfect vision in his left eye but his right eye was much weaker. The right eye, she said, was being "ignored by the brain".

The trial has heard that Ms Treacy and her brothers farmed about 140 acres at Derryhiney and that she came to own another farm at nearby Kiltormer. Following the deaths of Ms Treacy's brothers, Michael Scott came to own half the land at Derryhiney and Ms Treacy owned the other half. She leased her land at Kiltormer and Derryhiney to Michael Scott.

Witness Regina Donohue has told the trial that by Christmas 2017, the deceased had made an application through her solicitor to split the land at Derryhiney and put a new lease on the half that she owned.

On the day that Ms Treacy died, Mr Scott was to receive a letter from an agricultural consultant telling him that Ms Treacy was applying for a single farm payment on land she owned but had previously leased to Mr Scott.

Gda O'Connor will continue his evidence before Ms Justice Caroline Biggs and a jury of eight men and seven women tomorrow.