It's a procedural necessity though. In my jurisdiction there is a concept called "similar fact evidence" that might be introduced (extremely difficult though) in certain circumstances where previous behaviours and actions can be admitted into evidence. But the problem with routinely bring in priors is that a jury can be biased - even inadvertently - and see the evidence less than objectively. That would be unfair and fairness is an important part of a trial.
dI....i understand what you are saying......but if the person on trail has been arrested before NUMEROUS times (not once before,but 3,4,5,6 times before) and here he is again, on trial for the same thing.....and they already know the evidence is pretty heavy,not thin,but heavy against him......well in these cases i think the jury has the right to know...
It makes sense doesn't it? The problem is that common law systems aren't much interested in common sense. This has been a particular bugbear of mine for some time. I understand why things are the way they are but they shouldn't be that way.
I'll try to keep this brief.
The common law-influenced trial depends on the logic of inference.
To be able to infer you have to have something to infer from and that's where evidence comes into it.
The evidence, as we are all aware, can be of many forms but one thing it has to be is admissible.
Admissibility broadly depends on fairness in how evidence was obtained.
Plenty of evidence can be found by investigators but not presented because of the admissibility rules.
The propensity of an individual to, say, steal cars, might be represented in his priors but how much weight should the jury be allowed to put on his prior behaviour if he's on trial for a fresh count of stealing a car?
If the jury knew he'd been convicted fourteen times for car stealing I think they'd be inclined to think he'd done it this time too.
But would that then mean the jury would see the evidence differently?
Would there be a greater propensity for the jury to infer guilt from what evidence there was because of the knowledge of the defendant's priors?
I think the argument is that the jury should be allowed to make its judgement, its inferential judgement, without being put in a particular frame of mind relative to the defendant because of known prior behaviours.
The evidence in front of the jury is what's important. His fingerprints were found inside the car (because he forgot to set it alight), similarly his DNA is all over the interior of the car. That evidence speaks for itself, as it should.
As I said, similar fact evidence is able to be produced in courts here but only under very strict circumstances. "Reputing" a defendant is considered unfair and the procedural rules of evidence are built on - among other things - fairness, hence the concept of a fair trial.