russell ` rusty ' yates said his ex-wife 's actions were ` a result of her illness '
she systematically killed her children in their texas home in 2001 .
was convicted of capital murder in 2002 , but in 2006 was found not guilty by reason of insanity - after being diagnosed with postpartum psychosis .
mr yates maintains she is a good mother who loved her children .
slammed prosecutors for seeking the death penalty during the first trial .
he has since remarried and has a son .