All methods of assessing who commits crime are subject to societal biases (and largely the same set of biases, so you can't negate them by combining multiple sources). There's no unbiased oracle to consult for true criminal guilt.

And that is even leaving aside that many crimes are defined in ways that, while they are “objective” in the sense that term is used in legal jargon, actual guilt or innocence is itself fundamentally not an objective fact.