A thumbprint is biometric information

 

In the previous message you stated a sort-of warning that a thumbprint is biometric information. I suppose, but I don't understand danger here.

Yes. The warning was more ominous than the situation warrants.

A thumbprint is biometric information in the technical sense: it is a physical characteristic that can be used to identify you. But that does not mean that putting a thumbprint on your will creates some important new practical danger.

The distinction I'd make is:

• A password can be changed. If somebody gets your password, you replace it.

• A fingerprint can't be changed. That's why fingerprints are treated as especially sensitive data by privacy people.

• But somebody possessing an ink thumbprint on a legal document doesn't thereby gain the ability to unlock your phone, access your bank account, or impersonate you biometrically. Modern fingerprint authentication generally involves a digital representation and matching process, not simply presenting an ink impression.

• And fingerprints are hardly secret information. You leave them on glasses, door handles, cups, papers, etc. An ordinary thumbprint isn't a cryptographic secret.

There is a more mundane concern with a fingerprint on a legal document: identity/authenticity disputes. If someone later challenged the document, the print can provide evidence that you actually participated in signing it. In that respect, it is arguably helpful rather than dangerous.

So in the context of your Cambodian will-signing situation, I wouldn't regard the thumbprint itself as something you need to worry about. My earlier wording made the biometric aspect sound more consequential than it really is.

Personally I think it better than signatures, as it is harder to forge.

I agree, particularly for the purpose you're describing.

A handwritten signature is essentially a stylized assertion of identity, and a determined person can practice or copy it surprisingly well. A thumbprint has a much stronger connection to the actual individual. Even if someone tried to imitate it, reproducing the ridge detail convincingly is considerably harder.

There is also a nice legal-evidentiary distinction: the print doesn't merely say “this looks like Frank's signature.” It can say “this physical characteristic belongs to Frank.” That can make a disputed execution substantially easier to investigate.

The one qualification is that a fingerprint isn't automatically proof that the person voluntarily signed the document. Someone could theoretically obtain a print and transfer it, or apply someone's finger without consent. That's why witnesses, proper execution procedures, and—where appropriate—video or other evidence can still matter.

But as between signature alone and signature plus thumbprint, I'd regard the thumbprint as an additional authentication measure, not a liability. In your situation, I wouldn't hesitate over the biometric aspect merely because it is technically biometric data.