I promised to rant about prosecutors and now seems like a good time. :) I'm not a lawyer so these remarks should be taken in context with the rest of my layman's knowledge of legal history. (Leaving myself a neat exit in case some lawyer raises a logodemic argument outclassing me about the technical aspects of this subject.)
Prosecutors and defense attorneys, as probably everyone knows, go to law school to learn their trade. Now, from what I remember a law degree is not enough to qualify to be a lawyer, in fact it is not the actual license to practice law, which I understand you could still potentially get without going to law school, what's actually required is the state bar exam. (Don't even think about it though, you'll waste your money taking that bar exam.) But, in old law school teaching tradition, there were differences in the approach to teaching the ethics of prosecution and the ethics of defense. They were not originally the same ethics. The basic theory goes something like this:
A prosecutor represents the people of the state. As such he has a fiduciary obligation to seek the truth wherever it may lead. Hence, when a crime is committed and evidence is presented to him by the police, he becomes the first line of evaluation, where he has to make a decision and weigh whether there is enough evidence to justify a trial. So, that's why whenever you watch a legal drama on television, which sort of boils down the actual process in a fictional manner, the police bring some evidence of a crime, the district attorney looks at it and says "There isn't enough here to hold him, kick him loose," and the bad guy goes free for a time. The viewing audience groans because they watched the suspect commit the crime, so you have created that dramatic tension from conflict between what the DA character knows, which is only what the police give him, and what they saw the crook do.
Second round, our hero detectives come to the DA again and plead for a wiretap or search or something of the like. Now, we are into a realm where civil rights become important. A search has to satisfy the requirements of the Fourth Amendment which protects people from unreasonable searches and seizures unless a warrant is issued by a judge, or so the theory used to go (in practice, this has changed drastically especially since the passage of the Patriot Act.) So anyway, in those old TV shows when Fourth Amendment rights were still "in vogue," the DA would say "I can't take this to the judge, he'll turn it down because of insufficient cause." Audience groans again, and the crook can only be tailed around by the police who are waiting to catch him doing more to substantiate the original crime, even though every TV viewer knows he's guilty and what kind of moron is that DA anyway?
Third round, now the police decide to take the law into their own hands, and they sneak a guy in to do a wiretap without a warrant. Bingo, they hit the jackpot, they have enough evidence for probable cause, they act on the information, locate witnesses or evidence they didn't previously have, and it's enough to justify a search. Right? Wrong! This is called "Poisoned Fruits." The DA finds out about the illegal wiretap and chain of evidence from it leading to the witnesses and evidence to support the search warrant request. He says "This is poisoned fruits, the judge will turn it down if I tell him how I got this, and if I don't and the defense finds out later, the suspect will go free in a mistrial!" Audience tears their hair out. Is there any way to get this bad guy?
All of this is because the prosecutors under the old ethical theory taught in law school have to adhere to standards in their pursuit of truth -- remember, that means if they uncover disculpatory evidence, that is, evidence that proves the innocence of a suspect, they have the fiduciary obligation to set that suspect free, drop the charges, restart the investigation with another suspect, whatever it takes to get back on course with determining truth. The practicality following the ethics is, to have the truth on your side, you have to be on the truth's side, and that means following constitutional procedure and due process of law. You may want to win the case, but if you don't have the truth, and you win based on lies or by cheating on due process, you have committed an injustice.
Defense attorneys under the old theory are not bound by the same rule. Their fiduciary obligation is not to the people of the state, it is to their clients. They also must follow due process of law but their aim is to defend the civil rights of their clients and instill reasonable doubt in a jury, because their commitment is to win the case. Now, conservatives and prosecutors have pushed things to the point where this unfair advantage of the defense attorney, who only has to win the case, not worry about whether his case is based on truth, is to be reduced to the extent possible. They have had help in this regard by the fact that prosecutors have been able to campaign on their anti-crime successes (whether actual or not, whether ethical or not) to get themselves elected or appointed to judgeships.
Hence, there has been an increasing trend for judges to be friendlier to prosecutions and more hostile to defenses, leading to a loosening of common-law and constitutional restrictions on prosecutorial and police conduct. Also, as law schools import retired judges and prosecutors as professors, there is no longer so much emphasis on teaching budding would-be prosecutors that the most important aim of a prosecution is to arrive at the truth. Now the aim is to win, and law schools get vetted on their ability to teach lawyers how to win, regardless of whether they work for the people of the state or for a client. (It also hasn't helped that progressive education theory debased colleges from teaching ethics based on traditional Western philosophies, allowing them to adopt ethical frames of reference that are more relativistic than realistic.) So, now the technicalities and other constitutional pitfalls of a police investigation and a prosecution are being brushed aside, both by relativistic legal opinions and by changes in legislation that weaken the Fourth, Fifth, Sixth, and Seventh Amendments, to the point where they have now become seen as an irritating inconvenience to be swatted aside for the sake of public safety, instead of remaining the Supreme Law of the Land.
So nowadays the cops and robbers' shows, exemplifying art comically imitating life, regularly feature police officers and prosecutors running roughshod over civil rights because they almost always "know" who's guilty, or are REALLY GOOD at finding information, and because that dirty creep is guilty he deserves what he gets and the audience gets what it wants -- with the only real dramatic conflicts being about finding the bad guy, and you get these cookie cutter endings: the police shoot him as he reaches for his piece, or he gets browbeaten -- or literally beaten -- by some brilliant interrogator until he fesses up, confronted by all the evidence the police obtained illegally anyway and couldn't use until he corroborated it, or it's a Mr. Big situation where the bad guy is really rich and pays higher ups to cover him while he tries escaping to South America and gets caught by intrepid rebellious cops who cheated due process to find out where his flight was gonna take off from. The end justifies the means is the new message and practice. The reality is this is the beginning of a fascist dictatorship.