That would only work if the person in question hasn't covered or physically disabled their webcam.
Did you try doing a password reset on your parent's webmail account? I was able to do that to my mother's Yahoo account after she died (since she had set up her security questions with truthful answers), and I was then able to do the same for her Facebook account, which was tied to that email.
Granted, I had to actually ask one of my aunts for the answer to one of the questions, since it was about something we had never discussed, but overall it wasn't too difficult.
It was actually kind of humorous, since my mother always made a fuss about making me turn around when she would enter her password, and I would tell her that she was being silly, and that if I *really* wanted to get into her account, I could. Heh, I still get the mental image of the look on her face she would always get whenever something happened that enabled me to tell her "I told you so!".
The issue came to light ten days ago when one of our web developers discovered that, starting on about June 23, for a period of 30 days, a data sanitization process of the Mozilla Developer Network (MDN) site database had been failing, resulting in the accidental disclosure of MDN email addresses of about 76,000 users and encrypted passwords of about 4,000 users on a publicly accessible server. As soon as we learned of it, the database dump file was removed from the server immediately, and the process that generates the dump was disabled to prevent further disclosure. While we have not been able to detect malicious activity on that server, we cannot be sure there wasn’t any such access.
There is one way to find out if a man is honest -- ask him. If he says "Yes" you know he is crooked. -- Groucho Marx