I thought the testimony of one spouse against the other was basically inadmissible in court. I'm not a lawyer though, so I defer to you.
I am not a lawyer either....but I think you cannot compel them to testify.
from the internet.
” Testimonial privilege: in criminal cases, one spouse may refuse to testify against his/her defendant spouse. The witness spouse alone may choose to waive the privilege. 2) Communications privilege: in both criminal and civil cases, communications between spouses during the marriage are privileged.”