Two men have been accused of "staggering incompetence" in performing a contract killing on the wrong person.

Aamir Siddiqi, 17, of Cardiff, was stabbed to death on the doorstep of his home in April 2010.

Swansea Crown Court heard Jason Richards, 38, and Ben Hope, 39, were paid to carry out the killing but went to the wrong address.

Both deny the murder and the attempted murder of the student's parents, who tried to defend their son.

The court heard the intended target was a father of four who lived 70 yards (64 metres) away from the Siddiqi family.

The jury were shown a map of the family home in Ninian Road as well as a house in Shirley Road behind it, where their intended target lived.

Patrick Harrington QC, prosecuting, told the jury that Mr Richards and Mr Hope had been paid by a businessman, angry because a property deal had collapsed, to kill his chosen victim in Shirley Road.

But on Sunday 11 April they went instead to a similar looking redbrick, end-of-row house in nearby Ninian Road, he said.

It was, said Mr Harrington, a colossal mistake - a fatal mistake - for Mr Siddiqi, a student and hoping to study law at Cardiff University.

He answered the door to face a cowardly and brutal attack by two heroin-fuelled killers wearing balaclavas, said Mr Harrington.

Mr Siddiqi's 68-year-old father, Iqbal, and 55-year-old mother, Parveen, tried to stop the attack but were themselves stabbed, the court was told.

"They were unable to stop their son's murder," said Mr Harrington.

Mr Harrington said Mr Hope and Mr Richards had used a stolen Volvo car on the day of the murder, later found abandoned.

Image caption The prosecution said the defendants had 'contrived to create a case which blames the other'

Examination found traces of the teenager's blood in its footwell together with Mr Hope's fingerprints and DNA matching Mr Richards, he said.

The court heard investigators used Cardiff's CCTV network to trace the movements of both men before and after the killing.

The case against them also includes a large amount of evidence gathered from mobile phones allegedly used by both men, the court heard.

Mr Harrington said that after the brutal killing Mr Hope and Mr Richards were paid cash, before the alleged mistake in murdering the wrong person was revealed.

"Ben Hope went and bought himself a new pair of trainers and a laptop computer with the wages he was handed for murder," he said.

Within days both men were arrested and "each defendant has contrived to create a case which blames the other," Mr Harrington added.

He told the jury that the prosecution agreed with both men to the extent that "the killer is in the dock".

"They are both right," Mr Harrington added.

"Jason Richards is right when he said Ben Hope did the killing and Ben Hope is right when he said that Jason Richards did the killing.

"What happened is that they did it together."

The trial, which the court heard was a re-trial after the jury in a Cardiff Crown Court case last year was discharged, is expected to last for up to six months.

The case continues.