Why neutral expressions are preferred
Biometric systems compare stable facial landmarks. A relaxed face with the mouth closed makes the eyes, nose, mouth and jaw easier to compare across documents.
Country rules differ
The US State Department accepts a natural smile, but several other authorities ask for a neutral expression. If you are preparing one image for multiple applications, a neutral face is the safer option.
- US: natural smile may be accepted
- UK: plain expression, mouth closed
- Canada: neutral expression
- Schengen: neutral biometric expression