If you spend much time at the local police department, you might notice a steady stream of people coming in to give urine samples. In many cases, it is a condition of their parole or plea-deal that they submit to random sampling. They are sent a text and they have a certain amount of time to respond and submit a sample to show that they are drug free.
It seems reasonable to me that if a violent offender is offered leniency on the expectation that they will remain meds-compliant for anti-psychotic or antidepressants then a similar monitoring plan should be implemented as a matter-of-course.
It is amply documented that medicines used for mental health issues have a very high degree of patient non-compliance. The drugs have side-effects (weight gain, sleepiness, difficulty in climaxing during sex). The patient has little evidence that they are working (even if it is crystal clear to those around them). They will undoubtedly have a half dozen "friends" who tell them that they don't need no steenkin' drugs.
You might point out that there is nothing to stop the violent person from having a bottle of the pills available and taking one when he gets the text and then to lolly-gag as long as possible so it shows up in his urine.
I have no qualifications in pharmaceuticology but I believe that there are many substances that are partially metabolized by the liver and then excreted via the kidneys into the urine. I believe this is a MUCH slower process than the direct oral-blood-urine path. Five minutes of fishing around on the internet uncovered one such pathway "Glucuronidation".
I hate to give Big Pharma any more money, but it would be valuable to society if some of the heavy-hitters like Risperdone (currently off-patent and not profitable) were compounded with suitable "chemical urine markers" to indicate that the patient had been meds-compliant many hours before they got the text informing them it was time for their random urine drop.