Serious issues(spoilers)
1)How did the step brother know to cop to the 911 call? It certainly didn't appear the brother knew he would do it as he was terrified he was going to be the one called to the stand.
2)At the end when the detective realized Samuel Jackson was the killer she announced - "send a car to the house!". How did she get there before anyone else and kill Jackson? There were no patrol cars closer that would have gotten there before her?