In the US, it's "innocent until proven guilty".
Media is so quick to assume the person is guilty just because of an allegation.
Of course innocent until proven guilty applies but the justice department knows that and still brought charges. At the very least, they believe they've proven beyond a reasonable doubt his guilt.
High profile cases with public pressure change the equation a bit and can cause charges to be brought on people who normally would not. I suspect this is a way to pass the buck to the courts when the person eventually gets off due to lack of evidence.
It's a bit of a nitpick, but the Justice Department (DoJ) hasn't proven anything.
The defendants in question have been charged (and arrested?), but no trial (or plea bargain) has been held. As such, presumably the DoJ has what they believe is sufficient evidence to convict the defendants on the charges brought against them.
However, until a trial (or a plea agreement) is concluded, the DoJ hasn't "proven" anything. Rather, they brought charges against some folks. That's not "proven beyond a reasonable doubt," that's making accusations and bringing the case into the court system.
What the DoJ believes (and/or believes it can prove) is not proof in and of itself.