>> No, probable cause is not the same thing as evidence.
> Probable cause is based on evidence.
From wikipedia, "Probable cause" is a stronger standard of evidence than a reasonable suspicion, but weaker than what is required to secure a criminal conviction.
In other word, you can get a warrant when you don't have enough evidence to secure a conviction, which in turn may lead to gather sufficient proof of guilt (or exonerate the suspect, I suppose).
Yes, and any standard of evidence -- even reasonable suspicion -- can't be met without the existence of evidence. That's why its called a "standard of evidence".
Again, if there is no evidence left by the "hitman" except the calls for which the warrant is sought, as specified in the hypothetical, than there can't be probable cause to support the warrant. There can't even be reasonable suspicion. In fact, without some kind of evidence, the only thing that could support the desire to seek the wiretap is arbitrary prejudice.
Fair enough. However, if we take the original premise and change it to "If the FBI identified an organized crime hitman who killed 20+ people and left no solid, non-circumstancial evidence other than making incriminating phone calls, is it wrong for them to place a tap on his phone line once they have probable cause that he is a hitman?", would you agree that wiretaps (with warrants) can be useful?
Circumstantial evidence can be used for a conviction, so the absence of non-circumstantial evidence doesn't mean that there isn't evidence sufficient for a conviction.
And, even if the FBI could know that a hitman left a series of incriminating phone calls without already having evidence which could be admitted against the defendant of the content of those phone calls, a wiretap based on a warrant issued after the fact wouldn't recover those contents.
Further, I don't think anyone in the thread has argued that wiretaps aren't useful in criminal prosecution, the issue which started this was a poster expressing that it would be wonderful if wiretaps were categorically outlawed, which does not require believing that they aren't useful in certain circumstances. It could, for instance, proceed from the belief that the capacity is so likely to be abused covertly in circumstances where it is inappropriate if its existence is tolerated at all, that the usefulness it has in the circumstances to which it is appropriate is outweighed.
"would you agree that wiretaps (with warrants) can be useful?"
Nobody is arguing against that. What people are complaining about is, among other things, the bulk collection and retention of records; the gathering of records upto 3 degrees of separation from a suspect; etc.
> Probable cause is based on evidence.
From wikipedia, "Probable cause" is a stronger standard of evidence than a reasonable suspicion, but weaker than what is required to secure a criminal conviction.
In other word, you can get a warrant when you don't have enough evidence to secure a conviction, which in turn may lead to gather sufficient proof of guilt (or exonerate the suspect, I suppose).