[mongol]

Exactly. This is obvious. That is why law enforcement wants to perform interrogations in an environment they control, when they are dealing with a suspect.

[keithpeter]

In Europe, cooperation between different police forces is fairly routine. Below some examples from UK police forces, I'm assuming reciprocity.

http://www.dailymail.co.uk/news/article-184038/Police-smash-...

http://www.sussex.police.uk/about-us/policies-and-procedures...

(UK has around 40 regional police forces along with various national agencies.)