Ummmm...well, I'll take a guess and say...maybe because he wanted to see what a preliminary investigation would uncover.
It doesn't make sense to spend taxpayer dollars if you don't have to, does it?
Why don't you ask Sheriff Joe? Here is his phone number...again...Sheriff Arpaio: (602) 876-1801.
That way you don't have to ask people that you obviously have no respect for to opine on the issue.
Or perhaps it was a safe way out of a political problem. By going the posse route, he pleased his political supporters without actually doing anything of consequence.
If Sheriff Joe doesn’t have the money to investigate the crime of the century then perhaps he should look at what he is actually spending his money on.