On Monday the Dutch police distributed calendars with information of 52 cold cases to prisoners in five prisons. They hope that the prisoners will have information that can lead to new insights in the unsolved cases, the police announced on their website.

The calendars list known details of 52 unsolved cases, one for each week of the year. The cases were selected by the police's cold case teams. They are all cases that caused social unrest and in which the teams believe have a chance of being solved. Experience shoed that prisoners often have information about criminal offenses that haven't been solved yet. 

The idea of the calendars was borrowed from the United States, where every year several states distribute a deck of cards containing information about cold cases among prisoners. According to the police, dozens of cold cases have been solved thanks to this method. 

According to te police, there are about 1,500 unsolved crimes classified as cold cases in the Netherlands. Most of them are murders. Witnesses often play a crucial role in solving these old cases, Wim Perlot, leader of the Midden-Nederland cold case team, said according to NU.nl. "Recent research show that in the Netherlands there are an estimated 800 people with information about an unsolved murder or manslaughter."

"Hopefully this calendar encourages prisoners to share their knowledge about unsolved crimes with  the police", Justin Hammer, detective at the Oost-Nederland cold case team, added. "If we can solve one case, it will mean an end to years of debilitating uncertainty and ignorance for the survivors."

A reward was also issued for useful information for each of the 52 cases in the calendar. The reward varies by case, but the total amount is over 800 thousand euros. The calendar was also published on a special cold case page on the police's website.

The calendars were distributed in prisons in Leeuwarden, Zutphen, Sittard, Zwaag and Schiphol. If they prove successful, they calendars will be distributed in all Dutch prisons. This is part of a broader offensive by the police to draw attention to cold cases.