A list of body parts belonging to murder victims and held by all UK police forces is being created for the first time, it has emerged.
The Association of Chief Police Officers (Acpo) expects the nationwide audit to be completed in April 2011.
Forces in England, Wales, Scotland and Northern Ireland are all taking part in the exercise.
The samples have been kept for investigative purposes, Acpo said.
Assistant Chief Constable Debbie Simpson, the organisation's lead on forensic pathology, said the audit would allow police to identify appropriate ways of "sensitively dealing with tissue no longer needed for criminal justice purposes".
She said: "Following a suspicious or unexplained death, the police routinely use powers to retain material taken from bodies at post-mortem examinations.
"Samples are retained as part of the investigation to establish cause of death and for evidential purposes such as toxicology examination.
"In some cases material is retained for significant periods both as a requirement of the criminal investigation and in order to fulfil legal requirements."
ACC Simpson said the audit was prompted by the Human Tissue Authority's (HTA) decision to audit samples held by NHS and local authority mortuaries in April.
She added: "While samples held by police for the prevention, detection or prosecution of crime do not, by law, fall under the HTA, Acpo is co-ordinating an audit of human tissues in historical suspicious death and homicide cases among all UK police forces, to establish the current situation in terms of police holdings."
The HTA watchdog's remit only applies to England, Wales and Northern Ireland. Its independent analysis of hospital post-mortems - where consent is required - will be published next year.
Police are able to seize potential evidence, including body part samples, under the Police and Criminal Evidence Act 1984 but there are currently no legal limits as to how long they can retain the samples.
An Acpo spokesman admitted that some family members may be unaware the police had retained tissue samples of their relatives.
He added that if family members were suspected of potentially being involved in the crime, it was unlikely they would have been told about evidence that could be used in prosecution.
Post-mortem examinations on bodies where the death is suspicious do not need to have the consent of families and friends..
It is expected to be up to individual police forces to decide what to do with evidence they find that they no longer need to keep but feedback from the audit will be fed into an internal best practice document called the "Murder Investigation Manual".
The Acpo spokesman said the forces would deal with each case individually but any samples taken after the Human Tissue Act came into force would have been documented properly.
He said many of the samples were taken decades before there was implementation of best practice and the whole point of the audit was to gain a clearer picture of what was held and where.
The body is not anticipating major breaches in best practice guidelines.
Shaun Griffin from the HTA said: "We know about the Acpo audit that they are conducting and they are aware of our requirements."