In hindsight, the prosecution probably wished they didn't do that, since they are said to have had overwhelming evidence and proof, and there is even a Wired article about chat logs pertaining to DPR seeking services, but those are the breaks! If you don't do your due diligence, criminals can be let off on a technicality too!
They absolutely do that all the freaking time. Especially when other convictions already result in a long sentence.
Prosecutors have limited bandwidth, and just wasting time adding one more life imprisonment on top of a life imprisonment is not helpful.