My friend and I talked about that. Her speculation was the mother went into the room with the flashlight during the nightly "potty run," saw what was going on, went into a rage, aimed at the father's head and the father turned or arose. At that moment, the momentum from swinging the flashlight was in force and JonBenet was hit instead because the original target (the father) moved. This conversation was only a couple of weeks after JonBenet died so there wasn't much for outsiders to go on - we were just brainstorming because of mutual interest in these type things.
Remember, this was my friend's first speculation, not mine, and we were bouncing around ideas, so I can only address what we discussed. If you want me to ask her a specific question, just let me know. Her second idea was bed-wetting rage (this was long before Steve Thomas wrote his book). She told me bed-wetting is a common precursor to the rage that precipitates many cases of child abuse, particularly with over-stressed mothers who would not otherwise lay a hand on a child. At the time (January 1997) I told my friend that my suspicions were on the father being the killer or else the sibling was involved and both parents were protecting him. As you know, no one yet really knows and we were just two friends discussing something dear to our hearts - child protection.
I still think Steve Thomas knows of evidence that led him to conclude Patsy may have done this in a rage. Thomas's opinion, coupled with the skills I know my friend has in this area, makes me lean toward Patsy. I just wish we had access to the evidence locker.