What do you suggest if my special needs child (age: 14) won't stop pooping in her pants?

Depends : It's hard to discuss without knowing what "special needs" means. If he is a teenager that really should be able to control his bowel movements, it could be encopresis. Essentially it happens when a child is so constipated, that the stool leaks around the impaction. If that what it is, treatment is aimed at managing the constipation. I often refer to the gastroenterologist.