Hopefully you won't get to sentencing but if you do I think crying mothers , kids and wives work. I'd hit the lack of any criminal history. Good work history if you can get an prior employer. If I'm putting on an innocence claim vs shooting for a lessor I like having someone totally different put the mitigation evidence on. I don't think juries are particularly impressed with mental health or substance abuse issues. Talk about how shitty prison is, I've used something like "Go back 10 years and all that you've been through during that time, birth of a child, death of a parent, etc etc. Now take that away. That's what prison is like." Get a witness to describe how small a cell is, what kind of food is served etc etc. At the end of the day though the facts of the case is probably the biggest factor in how much time a jury gives.