A light-gold Toyota Corolla shipped from Kabul, Afghanistan, to a court house in Norfolk, Virginia, was the centre-piece for a jury trial last week on the alleged murder of two Afghan civilians on 4 May 2009 by two former employees of a subsidiary of Blackwater, the private military company.

Fareed Haji Ahmad, the driver of the Corolla that night, was also brought from Kabul to testify. He was injured in a hail of bullets fired by Christopher Drotleff and Justin Cannon, the two US citizens on trial for murder. His passenger Romal Mohammad Naiem was killed, as was a passer-by named Rahib Mirza Mohammad.

The Virginia jury listened to testimony from Karim Dad Mohibi, the Afghan bartender of the Oase German restaurant at Camp Warehouse who served beer to a group that included Drotleff and Cannon on the evening of the killings. The jury also stepped out of the court room to view the bullet holes in the trunk of the car.

"They were drinking. They were driving. They were armed and they were out of control," said Robert McGovern, an attorney for the US department of justice, which filed the lawsuit. "They were not soldiers and they were not on a mission. They were contractors who were making their own rules that night."

By coincidence, the murder trial opened almost exactly three years to the day that 17 Iraqis were killed by a group of Blackwater guards in Nisour Square, Baghdad.

Human Rights First, a New York-based group, says that these two incidents show why the government needs to strengthen the rules on oversight and coordination over private security contractors in war zones. "Congress and the administration must work together to put solutions in place before additional contractors are deployed," says Melina Milazzo, author of a new Human Rights First report titled "State of Affairs".

While murder is the focus of the Norfolk trial, and the question of whether the men were drinking and driving is another aspect of the trial, there are even more critical issues at stake – such as proper authorisation to carry weapons and the fact that the company may have taken the guns illegally from Afghan police stockpiles.

Cannon and Drotleff worked for company called Paravant, one of 30 or so subsidiaries created by Blackwater in the wake of the Nisour Square killings, in an apparent attempt to avoid the infamy that accompanied their own brand name. (Blackwater has even renamed itself Xe to distance itself from its past.)

Paravant officials did not have permission to carry weapons. (A 6 November 2008 email from Paravant vice-president Brian McCracken states: "I got sidearms for everyone… We have not yet received formal permission from the army to carry weapons yet but I will take my chances.")

In fact, Paravant had acquired the weapons from a place called "Bunker 22", where weapons and ammunition are stored for use by the Afghan National Police. A 19 November 2009 letter from General David Petraeus specifically confirms that "there is no current or past written policy, order, directive, or instruction that allows US military contractors or subcontractors in Afghanistan to use weapons stored at 22 Bunkers."

One of the most bizarre part of this story is the fact that Paravant had been hired for the specific purpose of teaching the Afghan national army how to use their weapons safely. Not that Cannon and Drotleff were role models – both had been discharged from the US Army and been in trouble for matters like reckless driving and testing positive for cocaine.

After the killings, Paravant claimed it had returned the weapons, but an investigation by the senate armed services commission in January 2010, showed that company officials were still in possession of the weapons.

Larry Dash, one of Cannon's lawyers, told the jury on Thursday that the men weren't properly trained, and they were scared because they were in an area where troops have been fighting a "nameless, faceless, merciless" enemy. Which suggests the question: if they weren't trained, what were they doing there in the first place?

Given that the US government has been ramping up the number of armed contractors in both Afghanistan and in Iraq, the Obama administration would be well-advised to pay attention to the Human Rights First report.