Case 1:
The police have caught a thief suspected of a string of robberies at convenience stores. Since he has refused to confess to his crimes during interrogation, the police decide to waterboard him to elicit a confession. He confesses to his crimes and goes to jail.

Case 2:
A suspected serial killer has refused to confess to his crimes during normal police interrogation. The police decide to use waterboarding to make the serial killer confess and disclose the location of dead victims that have not been found by the police. He confesses and is sentenced to death.

Case 3:
A child serial rapist has abducted a child. If the police do not find the child it could die. The police caught the suspect and decide to waterboard him. The suspect discloses the location of the child and is sent to jail.

Case 4:
A communist agitator has been organizing workers to join unions. He is also suspected of organizing demostrations against the government. The military capture this man and waterboard him to make him disclose the location of his associates. The man confesses and he and all his associates are sent to prison.

Case 5:
A man is supected of being a member of the communist party and organizing guerrilla operations against the government. He is captured and waterboarded to make him disclose the location of the guerrilla command and all of his revolutionary comrades. He confesses and is sent to prison. His comrades were never found.

Case 6:
An radical anarchist is suspected of carrying out bombings against banks. This has disrupted the businesses of banks and cost millions in property damage. He confesses to his crimes during waterboarding and is sent to prison.

Case 7:
A man is suspected of being a member of Al Qaida and of having information in a bombing that could leave hundreds of people dead. He is subjected to waterboarding, but refuses to confess claiming that he is innocent. During the course of investigation it is found that he is indeed innocent and he is set free.

I divided my cases as follows:

Case 1: a common criminal
Case 2: a dangerous criminal with no victims in imminent danger
Case 3: a dangerous criminal with a victim in imminent danger
Case 4: a political prisoner not implicated in acts of terrorism
Case 5: a political prisoner suspected of acts against the government
Case 6: a political prisoner commiting acts of terrorism
Case 7: a suspected terrorist who is later found innocent

So my questions are:

If waterboarding is not torture, why are the police and other law enforcement agencies not allowed to use it when interrogating prisoners (cases 1, 2 and 3)?

Why is waterboarding not used to put extremely dangerous criminals away (case 2)?

Is waterboarding acceptable to save a human life (see case 3)?

Is waterboarding acceptable for undesirable political views or political prisoners (case 4)?

Is waterboarding acceptable for any military action involving guerrilla warfare or insurgents (case 5)?

Are all forms of terrorism (including mere economic terrorism) a good reason to use waterboarding (case 6)?

What do we do is somebody is subjected to waterboarding and is later found innocent (case 7)?

I find that waterboarding is one of those areas that some people see as black and white, and other see as grey. I am curious to see some opinions.