research on insults and swearing in germany (Berlin)

hi - does anyone have any information about the legal issues concerning insulting someone in Germany? a former police officer and friend told me that in Germany it is illegal to curse or insult the police and they can take you to jail if you do - it's not considered a violation of freedom of speech even if what you say or does not induce violence or infringe on peace. he also informed me that if you insult a citizen s/he can take you to court. i am having problems finding information about this online in english. any one know of such information? i'm curious about this for my own research.