I can't make my mind up about that as to whether she was involved in the murder. I keep thinking about how it was said Becky fought for her life she must have been kicking and screaming and NM must have looked ruffled up afterwards. Its the two stun guns I keep thinking about why two? Then the little one, unless she was asleep I can't imagine SH being in the bedroom with him helping him with the child awake in her arms and I can't imagine her leaving little one downstairs on her own at the moment I am thinking she wasn't involved with the actual killing
RBBM
One reason could be that SH was supposed to (the plan) participate in Becky's kidnapping and later sexual assault.
The stun guns were purchased in SH's name & I thought I read that the couple had stopped for batteries (believed to be for the stun guns) either the day before or just prior to arriving at Becky's home that morning.
Why did they leave the stun guns in their home? Why not toss them into the bags, plastic boxes with everything else?
Perhaps, they forgot to take the stun guns the morn of the planned kidnap and had left them home by mistake. Perhaps, they purchased the wrong batteries.
Who knows?
I don't think they were able to use the stun gun/s that morning when Becky was confronted and she was thus able to give him/them a bit of hell.