What sways the courts in deciding sole or joint custody?

[1mommy]

Hello
My question of the moment is what sways the courts to change joint legal/physical custody to sole legal/physical custody?
I feel that I have a pretty strong case, but my lawyer says that generally courts want to permit parents to be involved in a childs' life if they express an interest in it. Here is what I have going for me
1) my ex husband has not seen our son in over 15 months.
2) My ex asked to see our son the last two Christmases (that's it) yet did not show. This last one I filed an emergency motion asking the court to relook at parenting time because my son is 4 and had not seen his father in excess of a year and did not know him. Court granted my request and went further and ordered 2 hours a day supervised visitation. Which my ex then did not use, but he paid over $1000 for another child of his to come visit him
3) Ex moved approximately 4/2005 and never notified me of it or new phone number so how can I contact him?? (finally did 6 months later)
4) Ex has admitted to living nomadically in an RV for approximately 6 months so he can "move to where the work is"
5) Ex is in excess of $6000 in arrears for child support plus
6) owes in excess of $2000 for his portion of medical, educational, and transportation charges.
7) Ex has called son twice in the last 7 months
8) has been incarcerated for his umpteenth DUI since last court proceeding (doesn't have a license due to felony conviction)
So given that he hasn't seen him, doesn't call him, is not being financially responsible for him, and has been incarcerated BUT claims he still wants to be in sons' life and participate in decision making (this is a control issue with him) is that enough to sway a court to giving me sole legal/physical custody?
Because it sure seems to me that it should be. If it isn't something needs to be relooked at in the court system because I can't see how a parent that irresponsible can be allowed to make life decisions for a child, especially when there is one parent who is responsible and makes the decisions and has been making them without the other parent because the other parent was gone, disappeared without a trace for a substantial time.

[Mr. Knowitall]

If your ex- isn't exercising his parenting time, what's the problem? Why waste the money on custody proceedings if he's already effectively giving you sole custody?