Who Will Shout First?

4 criminals are caught and are to be punished. The Judge allows them to be freed if they can solve a puzzle. If they do not, they will be hung. They agreed.
The 4 criminals are lined up on some steps (shown in picture). They are all facing in the same direction. A wall separates the fourth man from the other three.
So to summarize :-

Man 1 can see men 2 and 3.

Man 2 can see man 3.

Man 3 can see none of the others.

Man 4 can see none of the others.

The criminals are wearing hats. They are told that there are two white hats and two black hats. The men initially don't know what color hat they are wearing. They are told to shout out the color of the hat that they are wearing as soon as they know for certain what color it is.

They are not allowed to turn round or move.

They are not allowed to talk to each other.

They are not allowed to take their hats off.

Who is the first person to shout out and why?

Who will shout first?

Know that person here! 

Source 

Chance of Knowing Color of Hat

Here is the given situation! 

Well, there are 2 possibilities of answer depending on what combination of hats Man 2 & Man 3 are wearing. One thing is sure Man 4 has least chance for getting what he is wearing. His crime must be the most serious one!

Case 1 : If Man 2 & Man 3 wearing same color of hat.

In this case, Man 1 would immediately come to know that he is wearing opposite color of hat & would shout out. In simple words, if Man 2 & Man 3 wearing WHITE (or BLACK) hats, then Man 1 & Man 4 must be wearing BLACK (or WHITE) hats. Since there is no chance for Man 4 to see Man 2 & Man 3 but Man 1 could see Man 2 & Man 3, he must be first to know color of hat he is wearing.


Case 2 : If Man 2 & Man 3 wearing hats of different color.

Now here Man 2 has to be very intelligent (like the reader as he has chosen to read this further). In this case, there is no way for Man 1 to come at any conclusion as there might be WHITE or BLACK hat on his head. After waiting for a while Man 2 has to apply some logic & should think this in his mind.

'Since Man 1 is not shouting he must be unsure with color of his hat. He would be sure only in case if I & Man 3 wearing same color of hats. Since he is unsure; the color of my hat must be opposite of Man 3's hat.' 

Now the judge if he is honest would put criminal with least serious crime at number 1 (or  & 2) same color (or different) hats on Man 2 & Man 3.