A police force has been criticised for storing evidence in such a haphazard manner that potentially vital DNA samples were found nestled amongst tubs of ice cream in the department’s freezer.

Routine inspections of West Yorkshire Police revealed serious lapses in the storage of forensic samples and DNA that risked damaging the chance of prosecutions. Inspectors found that samples were improperly bagged, never disposed of, inadequately frozen, or lost altogether.

The report by Her Majesty’s Inspector of Prisons and Her Majesty’s Inspector of Constabulary said staff at police custody suites had even been confused about which samples belonged to which suspect.

Inspectors said management of the samples needed urgent attention to avoid undermining prosecutions. They visited police cells and accompanying facilities in Leeds and Bradford in October 2008.

The watchdogs said they were concerned about how officers were handling DNA, blood and urine samples taken in the custody suites, many of which would be used as evidence in prosecutions.

The report concluded that there was poor management of forensic samples and DNA, which needed urgent attention and could undermine prosecutions and public confidence.

The report said: “Policies and audit trails relating to the handling, storage and submission of DNA, blood and urine samples had not resulted in samples being stored correctly or dealt with expeditiously.

“Samples were incorrectly stored in fridges and freezers alongside ice cream, with some improperly bagged.

“This led to confusion among staff tasked with submitting samples so many were not submitted for analysis and had been allowed to remain in freezers for a number of years.”

The report highlighted particular concerns about a blood sample labelled as related to a deceased victim of a road accident which had either not been submitted for toxicology tests or properly disposed of if not required.

It said: “We were unsure whether it really related to a road death investigation or whether there was an error on the label.

“We also noted a number of historic blood samples relating to ’unconscious drivers’, which again appeared neither to have been analysed nor disposed of.”

The inspectors also questioned the security of samples which were put in fridges or freezers in insecure rooms.

“One freezer door was damaged and wide open, calling into question the integrity of the samples inside,” the report said.

“Samples in another freezer had been defrosted and it was noted on the exhibits themselves that this had occurred, yet they had not been disposed of.

“These practices were exposing the force to unacceptable levels of risk. The maintenance of public confidence in forensic evidence is crucial.”

David Crompton, West Yorkshire’s Deputy Chief Constable, said: “The report refers to one instance of ice cream being found in a fridge near forensic samples.

“These samples were hair, blood, urine and fingernail samples from people who had been eliminated from criminal inquiries - though they were of no further value and there was no intention of either subjecting them to analysis or putting them on the DNA database.”

Mr Crompton said more than 100,000 people are detained in custody by West Yorkshire Police every year, which is 300 per day. “Managing detainees is a very challenging task,” he said.

Times Recommends

• Margot Fonteyn: In her footsteps
• Forget beautiful people, let's have wonky Brits
• Fundamentalist brew: faith and power