What the accused has told the police will be usable by all sides equally in court.

And the side arguing against you will use your words to assist you?

German courts aren’t special. All courts work the same. You are innocent until proven guilty. You do not need evidence of innocence. All evidence is to prove guilt. The prosecution is attempting to prove guilt. Police collect evidence to prove guilt because proving innocence is not required. Both sides can use evidence collected, yes, that’s the same everywhere, but it’s not collected to prove innocence. You are assumed innocent. No evidence required. If evidence is being collected it’s specifically to be used against you to prove guilt.

It makes zero sense for police to collect evidence of your innocence, the state to charge you with a crime, and then argue you are innocent of that charge. You are assumed innocent. Arguments that you are innocent are not required. Evidence that you are innocent are not required. Statements that you make can’t be used to prove you are innocent. You are innocent by default. Statements that you make can therefore only be used prove guilt.