Difference "in court" / "at court"

[Farro]

Hey there!

I just can't find out what's the difference between (for example) "a man in court" and "a man at court". For example there is this expression/idiom "a friend AT court". On the other hand I find a lot of "(how to act) in court" sentences when I check google.
Could anybody please explain that to me? That would be fantastic! Thanks!

[Delfino]

http://oxforddictionaries.com/definitio ... Bcourt___1

Definition of a friend at court

a person in a position to use their influence on one’s behalf:

I knew that it never hurt to have a friend at court

How to act in court defines the expected behaviour at the location: court.
e.g. In the court room you are to respect the judges. ...

[Farro]

Thank you!

But I still don't really get it. I wasn't exactly talking about those two expression or the idiom "friend at court". More like : What's the difference between saying "People at court" or "People in court"?

[Delfino]

Präpositionen in Ortsangaben
http://www.englisch-hilfen.de/grammar/p ... _at_on.htm

[tiorthan]

In "at court" the "court" is rather an institution as opposed to a location wherein you can be.