[imaginenore]

This guy should not be a health professional.

"But helmets are not supposed to shatter" - not true. Many bike helmets are designed to shatter on impact, that's how they absorb the energy.

http://www.bhsi.org/standard.htm

[vog]

Why was this downvoted? To me this looks like a perfectly valid criticism.

[upofadown]

The cited page does not even contain the word "shatter".