Why do courtroom work groups resist efforts of public demands to get tougher on criminals and often subvert them?
I agree that there are many in the legal system who prefer plea-bargains to trials. This has less to do with the rights of criminals than the workloads of prosecutors and public defenders. There are more criminals than the system can handle. I don't think that all prosecutors and defense attorneys are lazy. I do think that sometimes pleas are encouraged for expediency's sake that are not in the best interest of the defendant.
The justice system we have established and the Bill of Rights it operates alongside were very specifically created in such a way as to insulate itself from all of the whims and fashions of public opinion.
If the prime motivation of a prosecutor is to satisfy public demands, as opposed to upholding and enforcing the law and assuring a measure of public safety, then it is more likely that individual rights will also be subverted. Public opinion sways with the popular breeze at any given moment, but the law is to remain somewhat consistent. I think those that work in the legal system understand this much better than the general public.
I assume that by "work groups" you mean prosecutors and defense attorneys and judges.
The reason they resist these demands is because getting tougher on criminals would lead to more work for them. These "work groups" would prefer to cut plea deals so that the cases could be disposed of quickly. This is easier on them, which is important because they have excessive caseloads.
Cracking down would require more and longer trials instead of quick plea bargains. That would really complicate the lives of the court workers.
I think that the wording of the question is interesting. In the end, I believe that many groups, such as the American Civil Liberties Union, are advocates for individual rights because of their belief that these entitlements are not negotiable. Their advocacy for the rights of the accused and those who are in jail are in the belief that all individuals should be afforded the protection of the Constitution. From its earliest inception the ACLU has been committed to acting on the side of the individual, and in many cases, against the actions of the government. This can be seen in its insistence against United States intervention in World War I. With such a history, the organization has stood in stark opposition to the public and others' demands to extract harsher punishment and more punitive measures when it goes against the Constitution's principles and ideas. It is because of organizations like this that all individuals are afforded rights, even when others are willing to undermine such ideas.