Crypto expert explains why bitcoin makes 'perfect record' for tracking down criminals

The disappearance of Nancy Guthrie has brought a renewed focus on the traceability of cryptocurrencies and their use by criminals following reports of alleged ransom notes requesting payment in bitcoin.

Guthrie, 84, was last seen on Feb. 1, when authorities believe she was kidnapped from her home. There have been reports about multiple alleged ransom notes demanding payment in bitcoin during the course of the investigation, now in its second week.

While bitcoin gained a reputation...