If monsters walk, it just means the defence did a better job than the prosecution, which is not an argument for restricting anyone's rights under the law, nor is it a knock against defence lawyers. O.J. Simpson was acquitted largely because defence counsel offered a statistical argument that was true, compelling, and irrelevant, and nobody on the prosecution side or the jury spotted it for the fallacy it was. The argument was that only one in about 2500 men who batter their wives go on to murder them, so O.J. was extremely unlikely to be the murderer, and that added up to reasonable doubt for the jury. In statistical terms, that's the wrong sample space. The relevant statistic is that of the battered wives who are murdered, 98% of them are done in by their husbands, which makes it almost certain that O.J. did it.