My husband has a five yr old son. When he was two we were granted sole legal and physical custody of him. His birth mother has always had a bad drug addiction is a conflicted felon and has spend a lot of time in and out of jail. When we had the custody papers drawn up she agreed to the terms. Such as going to therapy and doing a bonding assessment with him. Currently she hasn't paid a single month of child support she has gone to jail for not paying. She doesn't call to talk to him nor has she done any of the steps to see him. Her visitation would only be one weekend a month. I'm curious if there is anyway we could have her rights terminated if I was willing to adopt him. We fear that one day she may try something and in no way could she provide for him. He has special needs do to drug use while she was pregnant and some things she would do to him. We live in Missouri

Sure, if you apply to adopt him, termination of her parental rights would be part of the process. See an attorney there in Missouri about the details.