It's called an eye witness, one of the least reliable forms of evidence.
Yes, absolutely.
Usually, witnesses are issued a subpoena and they come of their own means. If a witness does not want to appear, law enforcement can be directed to bring the witness.
A "warrant' Is a legal document used by law enforcement to to apply to the court for a specific reason (arrest - search - seizure - etc). Witnesses STATEMENTS can be used in the wording of the warrant but a non-law enforcement witness cannot, by themselves, apply for a warrant.
Stop his boat immediately
As a citizen, you do not have a duty to act. You may ignore it if you wish, but most would appreciate if you assisted law enforcement.
I suggest you personally become better acquianted with grammar and the English language.
You can report any suspicious activity or crimes you witness to law enforcement agencies promptly. Providing any relevant information or evidence you may have can also assist them in their investigations.
Most law enforcement agencies use photography to preserve crime scenes for use in court, both to refresh officers' minds and present visual evidence. Here's the way most police photographers get their start.
Law enforcement was hampered by the widespread corruption of law enforcement officers and other public officials.
Law Enforcement Exploring was created in 1973.
offical law enforcement was lacking
A number of law enforcement agencies use the explorer program of the boy scouts to teach kids about law enforcement.