That won't work. The "worst possible abuse" is that someone bought the police, the politicians, the judge and the jury. I'm afraid nothing is going to save you from that.
The real world has no guarantees. There are no unbreakable rules you can build a perfectly secure legal system on. You have to draw a line somewhere and say everything under that line we have to trust works. And then keep checking it is working. The price of freedom is eternal vigilance and all that.
If you think the politicians are doing a bad job, I'd suggest getting involved to try and fix it. A bit like open source in general really.