I consider that an argument in favor of proportionality, not against. It illustrates how legal systems can be abused. The Al Capone case is ultimately a failur

I consider that an argument in favor of proportionality, not against. It illustrates how legal systems can be abused. The Al Capone case is ultimately a failure in rule of law, of sorts. If he was indeed the gangster that Al Capone the pop character was, the police failed to catch and prosecute him for those crimes. In light of that failure, they basically abused laws (and maximum sentences) to convict him for a different crime. We are open to that sort of abuse so long as prosecutors and police have big discretionary powers. If the average jail term for crime X is 1 year on parole, but the maximum sentence is 10 years in prison and the prosecutor plays a big role in determining which one it will be… that's open to abuse. If a prosecutor really wants you but can't prove your guilt, she can get you for something small and push for an oversized sentence. This basically bypasses the rule of law. In any case, I don't think the Al Capone investigation would have violated the proportionality principle. He was being investigated (I assume) for murder, racketeering and the like. That merits a big investigation. It failed, but it wasn't disproportionate. The only thing that was disproportionate was the sentence relative to the (proven) crime. Maybe the scale of the prosecution itself too. Police were investigating a major criminal. That investigation should be (and will be) well resourced.