Prisoner transport company Serco says its performance is thoroughly monitored.
A spokesman for Serco said its performance was subject to rigorous key performance indicators, independent inspections by the Office of the Inspector of Custodial Services, on-site monitors and parliamentary supervision, as well as being subject to Freedom of Information legislation.
"Serco contracts contain abatement regimes and where we are at fault these are implemented," the spokesman said.
"We are never complacent and take any incident seriously, conduct thorough investigations and ensure, where applicable, corrective or improvement actions are implemented.
"We report regularly to the department and our annual reports are tabled in Parliament.
"In the two years since we started providing court security and custodial services there have been some 60,000 individual transports and activities around the State with a success rate of 99.5 per cent."