Since I can't see your textbook reference, it's hard to tailor a response to your exact curriculum, but here are some general tips that may help you do this fun assignment.
As you're watching, take careful notes on the facts of the case. Include the details of the crime, all the evidence, all the suspects, and all the steps taken to investigate with the information at hand. Leave nothing out—even leads that don't go anywhere are part of the investigation and should be included in a summary.
To make sure you don't miss any important details, you may benefit from referring to the classic list of reporter's questions:
- Who: Who was the victim of this crime? Who was the perpetrator?
- What: What, exactly, happened?
- Where: Where did this happen?
- Why: Why did this happen? Is there an established motive?
- When: When did this happen? When was it discovered? When did the investigation take place?
- How: How did this happen? How do we know?
Most importantly, don't forget to stay objective in your writing. Since they're designed for entertainment, investigation shows often take one specific perspective on a case in order to draw in the viewers.