Police Scotland has been given special permission from prosecutors to carry out the one-off "deep clean" - but insists it will not be throwing away anything that affects a live case.
The new national force announced the move after inheriting stations and warehouses across the country that are clogged up with so-called "redundant productions" from minor cases that the Crown never expects to take to court.
The force reckons its deal - for all productions relating to summary or non-jury cases dating to before December 2011 that are not expected to be prosecuted - will see it dispose of one-third of the 4.5 million items it currently holds in storage.
Chief Superintendent Gordon Samson of Police Scotland's Criminal Justice Division said: "The disposal of these productions is routine 'housekeeping' for us, but not having done it regularly in the past we have some catching up to do.
"We are working in partnership with the Crown Office and Procurators Fiscal Service to allow this to be done.
"The items in question relate to summary [lower level] cases only that have been concluded and the property should be returned to owners or disposed of accordingly. There is no risk to live cases or further enquiry."
Some of the evidence cleared from stores will be returned to its owners. Other items will be disposed of, Police Scotland said.
The "deep clean" comes after growing concern about the huge stores of lost and stolen property and evidence Police Scotland inherited from its legacy forces back in April.
Stockpiles include £4m in cash in police safes and bank branches.
A review ordered by Police Scotland and partially published last week found the system of 73 stores across Scotland no longer has space for anything new.
Its author, Chief Inspector Hugh O'Neill, wrote: "The driver for this review is not purely for financial benefit, but can be traced back to a lapse in communication between Crown Office and legacy forces throughout Scotland on when to release productions for cases which have been disposed or abandoned.
"However, there will be a long-term financial benefit if this review is introduced and managed effectively.
"It is widely acknowledged that all legacy forces seize and retain far more productions beyond those that are ultimately utilised for evidential use.
"Therefore production stores are at full capacity and production keepers regularly have to utilise additional storage space within police premises, both inconveniencing local offices and increasing the risk to the force in terms of items being lost, damaged or evidentially compromised."
Chief Inspector O'Neill found a variety of systems in place to deal with the storage of evidence and lost and stolen property.
Some old forces, including Edinburgh-based Lothian and Borders, stored both types of items in the same place. Others, including Fife, separated them.
He added: "Processes are disparate, with some legacy forces unable to quickly establish exactly how much cash they have in their stores or how many productions they hold."
Civilian production managers under the single force have created a special forum to standardise evidence storage and lost and stolen property across the country.
So far, among other things, they have agreed new national measures on storing firearms and munitions and retaining evidence for major investigations.
The Scottish Policy Authority's Audit and Risk Committee is set to discuss the "deep clean" and other proposals at its next meeting.
An SPA spokeswoman said: "Members of committee requested a progress report from Police Scotland against a number of issues that have been raised with regards to the management of productions across Scotland. This report will be discussed at the next meeting of the committee."