Crash that killed four officers remains unexplained
Road collision experts do not know exactly what caused the vehicle carrying four police officers to lose control before its rear crashed into a low bridge and burst into a "fireball".
An inquest heard that speed alone could not explain the horrific crash and that there was likely to be several contributing causes.
The Kilkeel-based constables -James Magee (27) Kevin Gorman (24), Kenny Irvine (30) and Declan Greene (39) - died in 2008 as they worked beyond their shift to respond to a blue light emergency call to aid fellow officers.
As their three-litre armoured Mitsubishi Shogun 4x4 negotiated a sharp right turn along the Moygannon Road, Co Down, in the early hours of November 23, its rear wheels swung out, turning it 180 degrees, with the rear crashing into a low bridge wall.
The impact crushed the fuel tank, causing the fuel to ignite and jamming the doors, trapping the officers inside.
GPS tracking indicated that the vehicle's driver Const Magee was driving at 73.8 miles per hour 400 metres before the first visible signs of the loss of control.
However, Damien Coll from Forensic Service Northern Ireland said that there was evidence that the car had slowed to 49-58 miles per hour when it lost control at the bend.
"In my 31 years of experience investigating these accidents, I have never found one single factor that contributed to a fatal collision," he told the inquest.
The accident's former investigation officer paid a moving tribute to the four men yesterday.
Former police inspector Ian Kennedy told the men's families: "These police officers paid the ultimate price (of serving the community) and you should be proud of each and every one of them."
The Belfast inquest heard detailed reports and conclusions from collision experts giving evidence on behalf of the court, the men's families and the PSNI.
Despite simulated road tests at the crash site and by nationally-recognised experts in England, there were a number of possible contributing factors which may have caused the loss of control,
Other possible contributory factors included the handling of the vehicle, tyre tread and a possible loss of road grip due the car going over a metal inspection cover at the bend, and inadvertent over-steering or over-braking by the driver.
The hearing continues.