If you think it is easy to prosecute a super-villain, think again. While Spider-Man comic books and films "throw the book" at super-villains rather cavalierly, real-life prosecutions of Dr. Octopus or the Green Goblin would be much harder. Simply put, Spider-Man's methods make the job of a criminal defense attorney a lot easier.
The Classic Spider-Man "Web and Note" Ploy
Spider-Man has a classic modus operandi consistently repeated when he captures villains. He wraps them up in a web, suspendsthem from some overhead structure such as a traffic light, and leaves a note mentioning the crime the person committed. To add some context and credibility to the capture, the note is signed by "Your friendly neighborhood Spider-Man."
Could this lead to a conviction? Yes, and the person convicted would be Spider-Man. Unless there is an arrest warrant or other proof of a crime, the super-villain captured in the web is not likely to be charged much less tried.
As for Spider-Man, the mere fact he left a note is an admission to a host of crimes including (possibly) kidnapping, unlawful detainment, disturbing the peace, aggravated assault, reckless endangerment, and more. Vigilantism is illegal.
Then again, Spider-Man does have a secret identity and this works both for and against him.
The Pros and Cons of a Secret Identity
Spider-Man would not be charged with a crime. Peter Parker would be since Spider-Man is nothing more than an alias. Unless the prosecutor can prove Spider-Man and Peter Parker are one in the same, no charges can be brought forth.
Unfortunately, in many instances, the only (seemingly) credible witness to a mad villain's crime is Spider-Man. Unless Spider-Man is willing to reveal himself as Peter Parker, a super-villain can take advantage of the confrontation clause. Under the 6th amendment of the Constitution, defendants have a right to face their accuser.
Leaving a note accusing someone of a felony is not going to cut it. Spider-Man would have to testify in court. And yes, the criminal defense attorney for even a megalomaniac such as Dr. Octopus has the right to conduct a cross-examination. If a conviction hinges on Spider-Man's testimony and the hero chooses not to take part in the proceedings, well, things may never make it past the grand jury stage.
Unless there is other evidence that can be legally entered.
The Legality of the Evidence
Last, questions may arise about the legality of the evidence. Could a doomsday ray gun created by Dr. Octopus be admitted into court if it was obtained illegally? The answer is no. Defense attorneys (such as those from Brian Walker Law Firm, PC) could argue that law enforcement agents who receive evidence from Spider-Man are receiving illegally obtained evidence. A judge may very well rule the evidence is inadmissible.
Spider-Man does a nice job of dealing with the immediate threat of a super-villains antics. No one would deny that. The ability to prosecute a super-villain captured by Spider-Man, however, is not exactly easy for a prosecutor.