The brakes of a tipper truck which crashed and killed four people, were "unusually hot" after the crash, a court heard.
Mitzi Steady, aged four, Robert Parker, 59, Philip Allen, 52, and Stephen Vaughan, 34, died in the crash on Lansdown Lane in Bath in February 2015.
The court was told parts of the braking system were "fractured or loose" and would have failed roadside tests.
Driver Phillip Potter denies causing death by dangerous or careless driving.
His boss at Grittenham Haulage Ltd, Matthew Gordon, 30, of Dauntsey, who was driving another truck in front of Mr Potter, also denies 14 offences; while the truck company's mechanic, Peter Wood, 55, of Brinkworth, denies four charges.
Gary Ford, of the Drivers and Vehicle Standards Agency, described how he examined the vehicle four hours after the accident and found one of the brakes to be "unusually hot" at 62C (144F).
But, he said, one other brake was just 5C (41F) suggesting it was "doing nothing".
He also told the jury that some of the reaction brackets (part of the braking system) "were fractured or loose" and in such a poor state of repair that the lorry would "have been taken off the road in a standard roadside check".
A former driver at Grittenham Haulage Ltd previously told the court he had experienced brake failings, electrical faults and air pressure faults.
In one incident, he said he felt the brake go "straight to the floor" as he attempted to stop behind a car making a sharp turn. He described the brakes as having a "spongy sensation".
The lorry hit several pedestrians, including Mitzi, from Bath, and a car containing Mr Allen and Mr Vaughan, both from Swansea, and Mr Parker, from Cwmbran, south Wales.
Phillip Browne, who lived on Lansdown Lane, told the court last week he heard Mr Potter describing what happened immediately after the crash.
He said he heard the driver say: "I think I've killed them. I was coming down the hill. I put my foot on the brake and there was nothing there."
Mr Potter, 20, of Dauntsey, is also charged with causing serious injuries to Karla Brennan and Mitzi's grandmother Margaret Rogers by dangerous driving.
He denies a total of 10 charges against him. The trial continues.