What Should You Capture: Snapchat
If you want to capture the profile information of whoever posted the message, click on the person’s screenname to be taken to their profile page. This should include name, profile picture, and other public information. Take a screenshot along with screenshots of their comments / activity. Also make a note of the date that you took the screenshot or screencast.
If you need to capture other peoples’ Snaps and Chats:
You can take a screenshot or screencast, but the sender will be notified. You also can choose to save a Chat, but again, the sender is notified. This may not be safe if saving will alert the abusive person that you are documenting their behavior. You should consider your own situation and whether alerting the other person that you’ve saved the information could be dangerous for you.
Alternatively, you could take another phone or camera and take an image of the content that the person sent you. Note: you should only do this if attempting to preserve abusive, threatening, or unwanted content. Other private content that is sent shouldn’t be saved or shared without the person’s consent.
Try to show the whole story to provide the context. This means you may need to capture your messages or recordings as well.