https://en.wikipedia.org/wiki/Criminal_Copyright_Law_in_the_...
> federal prosecutors filed a superseding indictment adding nine more felony counts, which increased Swartz's maximum criminal exposure to 50 years of imprisonment and $1 million in fines.[13][101][102] During plea negotiations with Swartz's attorneys, the prosecutors offered to recommend a sentence of six months in a low-security prison, if Swartz would plead guilty to 13 federal crimes.
Here's one that walks through the process:
https://www.popehat.com/2013/03/26/cloudy-with-a-chance-of-s...
Here's another, more hyperbolic one, showing how a claimed "facing 67 years" turns out to be more like "facing 24 months, and probably less than that":
https://www.popehat.com/2013/02/05/crime-whale-sushi-sentenc...
But the short version is that describing a criminal case as "facing up to 50 years" is like describing a lottery ticket as "worth up to 50 million dollars", and you should probably believe both statements about equally until the sentencing happens (for the criminal case) or the winning numbers are drawn (for the lottery ticket).
If it was an unbiased roll of the dice that would be one thing, and the average and the distribution would be meaningful. But when it's arbitrary it doesn't matter what anyone else got, only what you'll get. And if you have any complaints about your treatment, etc, you're immediately in the full-penalty group.
Everything I've read says the judge is the one who applies the sentencing guidelines. Prosecuting attorneys don't sentence people, as far as I'm aware.
But yeah, after that it's all the judge.
I'm pretty much in the camp that the DA would fuck you up and the police and judge would all be in on it. Try telling a cop what the law is, especially if you're right...
As you would expect most don't take that gamble.
Also, I assume the multiple counts issue also applies to Germany and other countries, so the US penalties aren't necessarily that much worse. (Well, 10 years is much worse than 5 years, but it isn't decades worse.)
If there are seperate trials (even for totally seperate crimes), the sentences are also combined as per above at the later trial (unless the former sentence was already executed).
As far as I know this is not unusual worldwide. Certainly other European countries use a similar system.
[1]: Wikipedia tells me that the US system doesn't ask that question at all. I know absolutely nothing about copyright cases in particular but e.g. starting a filesharing client that distributes many files to many people is still a single criminal act in Germany (civil law is different of course).