India, Sept. 21 -- In Goa, a woman was allegedly subjected to what has come to be known as a "digital arrest". But the bigger danger may be more unsettling: when anything can be faked, even genuine evidence can be dismissed as fake.

For decades, the most basic test of reality was also the simplest: seeing was believing.

A photograph showed what happened. A video captured an event. A familiar voice on the telephone established who was speaking. A person appearing on a video call was, by and large, the person on the other side.

That certainty is disappearing.

In Goa, a woman was allegedly subjected to what has come to be known as a "digital arrest". She was made to believe that she was under investigation, kept under continuous surveill...