Are you really implying that a prosecutor's threat to put you in jail for 30+ years wouldn't motivate you through emotions?
This thing of focusing on the maximum possible sentence is a bad habit inculcated by the media. It's more instructive to look at the median sentence for this kind of crime.
However, my point was to note the contradiction in you saying that prosecutors can't be swayed by emotion, while they conduct themselves so as to sway their targets with same. If you don't think that the threat of a long prison sentence would spur emotion in the person receiving the threat, well, I don't know what to say.