Grandmother ill and needs son to care for her; the son is incarcerated.

It appears that you need to write back with more facts.  If the son is incarcerated on pending charges, then his attorney can file a motion to reduce bond, and use the fact that the defendant is the sole caregiver for his grandmother (who is in poor health), as a basis for the motion.  On the other hand, if the son is incarcerated on charges which have been found guilty and a sentence has been entered, then it is very unlikely that he will be released due to his grandmother's health.  In any event, it is clear that the son needs a skilled defense attorney to determine whether any strategies exist to obtain a speedy release.  Good luck.