The "wiggle room" built into the lega system is because reasoning of any sort is always carried out under conditions of epistemic uncertainty. This is built into legal systems through concepts such as burden of proof, reasonable doubt etc. that acknowledge that the legal system makes mistakes frequently due to a lack of, or distorted information, and therefore there should always be avenues through which decisions can be challenged.

The second concept that is embedded (at least theoretically) in legal systems is the concept of procedural justice, that an outcome is Just iff all participants in the procedure that led to that outcome consider it Just. The most obvious example of this is trial by a jury of your peers.

In light of this you can see two obvious problems with these types of algorithmic systems. First they tend to treat the model as perfect and are used as if they can spit out guilty / not guilty answers by the people using them, and second they are often black boxes where it is impossible for the subject to challenge the outcome, as they don't know how it has been reached.

Ultimately I think these systems need to have a human in the loop and to be reasonable (in the sense that they can be reasoned about)