michelle heale of new jersey claimed she was trying to burp mason hess .
but jury said she killed him by snapping his neck as he was choking .
was charged with aggravated manslaughter and endangering a child .
sobbed uncontrollably as the verdict was read out and said : ` i did n't do it '
turned to her husband and asked him to make sure her five-year-old twins do n't forget her .
she faces up to 30 years in prison when she is sentenced next month .