Your honor, it is my opinion that my client Patrick Bateman has indeed killed many, many, MANY people, but we'd be better off not prosecuting him because would you just imagine how long it'd take?
This is of course why prosecutors will choose sometimes to carve off a few crimes where they're pretty sure they can get a conviction and will be enough to put the accused away for the rest of their life.
For instance, Robert Pickton, who was accused of murdering a few dozen prostitutes, was ultimately only found guilty of six counts of second-degree murder. (The Crown wanted first-degree but the jury only gave second-degree... but recommended the maximum penalty anyway, life without parole for 25 years, consecutively for all charges, which would have been mandatory for first-degree.) That got him in jail until he's dead, and the Crown stayed the other charges to save court time. (Over howls of protest from the families of the other women with whose murders he was charged.)
There's also at least rumours that Luiz Inacio Lula da Silva, former President of Brazil and, at one point, leading contender for the Presidential election last year, was nailed on a relatively minor corruption charge (as opposed to more serious ones he was facing) shortly before the election because his political opponents could get a conviction on that one much more easily, and all they needed was a conviction on basically anything to stop him from running.