This remakes the point that principles (and rights) compete for territory. And it is why you can't easily resolve these sorts of issues by saying one person's rights are more important than another person's.
In the UK, protections are generally provided as a result of custom and its interpretation.
The American Bill of Rights based model runs into these difficulties again and again because it largely fails to acknowledge the issue of overlapping rights.
In the end, a society makes choices which are not entirely tuned into a purist view of rights. Sometimes the need to reveal criminal behaviour is more important than the wish for genetic privacy.
Luckily for the US, this is acknowledged in the Fourth Amendment.
Or put another way, if there's probable cause, the police can take a sample of a suspect's DNA.
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