here's abc's derrick dennis. >> this morning, new allegations in the case of corey richards. utah mother accused of killing her husband, eric, by poisoning him with fentanyl, then writing a children's book on dealing with grief. investigators now claim richards may have had help from her mother, lisa darden. darden spoke about the case late last year and claimed eric may have accidentally overdosed on his own. >> i believe eric may have gotten pain pills and didn't realize that they had fentanyl in them would never, ever do this. not only to eric, but to those boys. >> newly unsealed documents reveal lisa darden was living with a woman back in 2006, who also died suddenly from an overdose, investigators now say based on lisa darden's proximity to her partners suspicious overdose death, it is possible she was involved in planning and orchestrating eric's death. corey richards attorney responded saying the fact that miss darden significant other was one of the millions that suffered from and ultimately succumbed to opioid addiction, is hardly suspicious. it is tragic and unfort