If you have a strong disposition for truly gritty and graphic shows, try Black Butterflies from France.  It's on Netflix and one of the best longitudinal serial murder/crime programs I've seen in a while.  It baffles me to hell how very few have commented about this limited series. 

A few years ago I got into programs described as Nordic Noir. There are a ton of them that are really pretty good - from Bordertown to Vahalla to many others.

Then, there is Iceland's Trapped and another show called Fortitude (that is better in the earlier seasons than the off the rails later one).

Also, Crime by Irvine Welsh.  Two seasons of excellent acting by Dougray Scott.

Another show I have seen very little mention of is Netflix's Criminal series.  This is a series that portrays fictitious criminal interrogations in different countries and I'll share this - if one thinks a show that is mostly filmed within an interrogation with just talking would be boring, well, this series shows otherwise. 

And to throw out some period decadence, there is Paris Police 1900 and Paris Police 1905.