Byzantine rules regulating the sale of used cars in Iraq have hamstrung investigators hunting the owners of vehicles used as car bombs in a wave of violence last month, police say.
The surge in violence meant May was Iraq's deadliest month since 2008, with the UN warning that unrest was ready to "explode" amid widespread fears of a revival of the country's brutal sectarian war.
At least 34 car bombs exploded during the month, and the authorities are now struggling to identify the owners of vehicles used to launch the wave of carnage.
Investigators blame the rules governing the sale of used cars. These were initially put in place as a temporary measure during the chaos that followed the 2003 US-led invasion but have yet to be fully phased out.
"The security forces have managed to get some licence plate numbers for the cars that were blown up," a senior security official told AFP, speaking on condition of anonymity.
"But we are facing some difficulty in finding their owners."
"Some of these cars have been sold more than a dozen times. When we start searching, we end up with no address for the actual owner."
Iraq was flooded with new cars after 2003 when import duties were slashed, but many were driven for months without any registration documents.
Authorities eventually put temporary measures in place, issuing interim black licence plates to cars bought after the invasion, instead of the white number plates that were prevalent beforehand.
It had been planned that those measures would quickly be phased out, but they stayed in place for several years.
Setting up a vehicle registration database took longer than first mooted, which meant owners selling their cars were unable to fully transfer ownership under the interim system.
Instead, buyers and sellers exchanged notarised court documents indicating the change of ownership -- and the more times a car was sold, the longer the paper trail.
Signup to our newsletter and follow us on Facebook and Twitter!
While a new system has been put in place for newly purchased cars, those bought in the interim have yet to be properly registered.
As a result, the authorities have no centralised database identifying the current owners of an estimated 600,000 cars bought in the interim, and many of these have been sold on several times.
Security officials say many of vehicles used as car bombs in the recent wave of attacks were bought in that time, bearing black licence plates, making it difficult to identify their owners.
Tough new restrictions have now been placed on cars with black plates in an attempt to combat the rise in violence.
This has caused problems for many with interim plates, among them taxi driver Mohammed Karim.
"The slow pace of the registration of vehicles is a big joke," the father of three said.
"These restrictions have hurt my livelihood instead of punishing a government which has failed to record the details of these cars for 10 years."
Others have suffered even worse knock-on effects.
A week ago, police investigating twin car bombings in the Habibiyah neighbourhood on May 27 questioned Emad al-Azzawi and searched his house, alleging that his black-plated car had been used.
Azzawi, a mechanic, told AFP by telephone from a police station in Baghdad that he produced paperwork supporting his claim that while he was the vehicle's original owner, he had sold it on.
But police were apparently unable to locate the most recent driver and instead arrested Azzawi, as the documented owner of the vehicle.
Asked about his case, a senior security official said Azzawi would probably be released, but human rights groups say systems of arbitrary arrest and long periods of detention without charge are rife within Iraq's justice system.
The lack of proper registration systems for cars on Baghdad's streets has caused government concern as well, with deputy interior minister Adnan al-Assadi claiming the police were using every available resource to identify the owners.
But in a television interview, Assadi admitted that the lack of a centralised system for tracking vehicle ownership was a "major security defect".