Error analysis is a method commonly used to identify the cause of student errors when they make consistent mistakes. In this context, it is the students who are analyzing either the teacher's justification or another student's justification.  It is difficult for students to judge the quality of their own math justification unless they have first spent time analyzing someone else's justification.  Having a discussion with students about how the justification could be improved for a particular solution can be used in conjunction with Review & Preview at the beginning of the class period.