The storage of forensic evidence at police stations in North Yorkshire has been criticised by inspectors.
There were problems with the handling of DNA and other samples at custody suites, said a report by the chief inspectors of constabulary and prisons.
It also highlighted a lack of mental health support for people in custody and identified weaknesses in measures to prevent suicide.
Despite the need for some improvements standards were "broadly positive".
The inspectors' report covered North Yorkshire Police's 24-hour custody suites at York, Harrogate, Scarborough and Northallerton and two part-time suites at Skipton and Selby.
Overall, it found that detention was well-managed and there were some areas of excellent practice.
However there were also areas for improvement.
"There were problems with the storage and handling of DNA and forensic samples at most of the custody sites," the report said.
"Some samples dated back to 2007, while others were undated and/or not stored in date order.
"The force needs to review their policies and procedures urgently to address these problems."
Healthcare services had just moved to a new contractor and the inspectors found the management of medicines "generally unsatisfactory" and mental health services "underdeveloped".
The report said: "Apart from Scarborough, there was no contractual provision of mental health support."
Self-harm and suicide were covered in initial custody training but few staff had received refresher training, the inspectors said.
"Staff did not carry anti-ligature knives, but these were kept behind the custody booking-in desk in all suites except Selby.
"There were some ligature points in cells and other detainee areas, despite the recent refurbishment."
Assistant Chief Constable Tim Madgwick, said: "As with any inspection there are improvements to be made, but overall we believe that North Yorkshire Police provides cost effective, professional and appropriate facilities for the safe detention of offenders and for the management of investigations and offences.
"Some issues raised in the report were dealt with and rectified immediately, with plans in place to address other areas of feedback which will be monitored by the inspectorate over the coming months."
"The force recently carried out a custody refurbishment programme and we are very pleased that the hard work and investment by the force and North Yorkshire Police Authority has been acknowledged.
"Another area singled out for praise was that of standards and attitudes of our staff, which is a pleasing reflection on the efforts and professionalism of our workforce and our high standards of training."