ASK A PRO: Dutch Inmates to Be Given Cold-Case Calendars in Drive to Solve Crimes.

The Dutch police announced the project last week after a pilot program that rolled out in five prisons in January coincided with a large number of tip-offs.

“We got 160 tip-offs in the first five months of this year and we normally get 160 a year,” Robbert Salome, a spokesman for the Dutch National Police told NBC News. Jeroen Hammer, who helped develop the calendar, told Dutch broadcaster NOS that the tip-offs had allowed police to reopen two cases out of the 52 featured on the calendar.

Salome said that while it was impossible to know how many of the tips had came from prisoners — because the informants have the right to anonymity — research has shown prisoners knew a lot about other crimes.

“We know that people in prison talk about crimes,” he said, adding that a study had shown that in 40 percent of court cases in the Netherlands, the perpetrators had told someone about the crime they had committed.

Officials had better do a perfect job of protecting prisoner anonymity, or the program will descend into payback and blackmail.