The legal world is, officially, very humble. It isn't a fact that someone robbed 10 banks. It is a fact that they were /convicted of/ robbing 10 banks. The legal system isn't perfect, lots of basically guiltless people get chewed up by the machine. An acceptance of that reality permeates a lot of legal practice (embedded in the system, although I expect a lot of lawyers get it too).
How is a person's history not a fact?
The key word you are missing is relevant fact. Some very great minds have put a lot of effort into making the legal system robust against the unreliability of all the evidence that passes through it. The rules regarding evidence in the Common Law tradition are quite well thought out. A case starts by gathering evidence of what transpired, proceeds by assessing it against some standard and finishes taking a (more or less) predictable action.
If someone has 10 convictions, they have received an appropriate treatment for what they have done. Imagine that a bank robbery has occurred and someone has a history of 10 bank robberies is the suspect. If the case is borderline, and the 10 prior convictions is what pushes it over the edge, then this is effectively the same as further punishment for past misdeeds.
If the 10 past misdeeds are acceptable evidence, then it is equivalent to punishing someone further for past crimes. That isn't acceptable - the sentence at the prior conviction is meant to be the end of the matter and to allow otherwise violates principles of fairness. For reason of fairness, they can't be accepted and the current case must be tried on the merits of only evidence about that instance of crime.
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Ok. IANAL :)
The legal world is, officially, very humble. It isn't a fact that someone robbed 10 banks. It is a fact that they were /convicted of/ robbing 10 banks. The legal system isn't perfect, lots of basically guiltless people get chewed up by the machine. An acceptance of that reality permeates a lot of legal practice (embedded in the system, although I expect a lot of lawyers get it too).
The key word you are missing is relevant fact. Some very great minds have put a lot of effort into making the legal system robust against the unreliability of all the evidence that passes through it. The rules regarding evidence in the Common Law tradition are quite well thought out. A case starts by gathering evidence of what transpired, proceeds by assessing it against some standard and finishes taking a (more or less) predictable action.
If someone has 10 convictions, they have received an appropriate treatment for what they have done. Imagine that a bank robbery has occurred and someone has a history of 10 bank robberies is the suspect. If the case is borderline, and the 10 prior convictions is what pushes it over the edge, then this is effectively the same as further punishment for past misdeeds.
If the 10 past misdeeds are acceptable evidence, then it is equivalent to punishing someone further for past crimes. That isn't acceptable - the sentence at the prior conviction is meant to be the end of the matter and to allow otherwise violates principles of fairness. For reason of fairness, they can't be accepted and the current case must be tried on the merits of only evidence about that instance of crime.