Most people, conservatives in particular, would say that the Miranda case has harmed law enforcement. They would say that it has handcuffed the police by forcing them to do all sorts of procedural steps that get in the way of actually trying to get at the truth of what has happened in a given case.
There are some, though, who would argue that Miranda has forced police departments to improve themselves. It has forced them to try harder to actually find evidence against accused criminals rather than trying to bully confessions out of them.
There is no way to objectively say which of these points of view is more true.
When Justice Warren presided over the Miranda case, it represented a moment where the rights of the accused were articulated as being protected under the Constitution. The Miranda case transformed law enforcement procedures and practices. It forced law enforcement officials to be more vigilant regarding how they arrested individuals and how they treated those who were accused of criminal activity. The Miranda case ensured that if procedural due process standards were violated, criminals could appeal on those grounds. We now have a tendency to view Miranda as something that has the potential to handicap law enforcement officials. Yet, the intent behind the case was to make sure that law enforcement officials represent the highest of ethical and legal conduct because they are the standad to which all other aspire in our society. Rather than cripple them, Warren's decision in Miranda actually raised them to a standard and position whereby their actions could be placed under the harshest of scrutiny in order to ensure that procedural due process is upheld at all costs.