What Was the Legal Status of "Wanted - Dead or Alive" in the Wild West Days? (Assuming those posters weren't a creation of Hollywood)

Kenneth Anderson wants to know:

• First, to what extent was this actually a historical practice [in 19th century frontier days], or is it really just a creation of Hollywood westerns– any scholarship on this, or actual examples?
• Second, from the standpoint of the law in force in that period, on what basis was this kind of “dead or alive” language used?
• Third, what was the relevant Constitutional doctrine of that day and did it have a role to play?  Why or why not?

See also the comments to his post on The Volokh Conspiracy.

What a great ALR assignment! Certainly could take law school students beyond WEXIS to perform research. [JH]