When an analyst looks through some images they have to make a subjective judgement because it is very hard to judge age in many cases.

To be clear; striking a suggestive pose is very very rarely illegal in itself. It may be classified on a relevant scale as part of the investigation (e.g. COPINE) but that is only because it is of obvious relevance to the charge/conviction.

If someone was caught with "suggestive" images on their computer in the UK, for example, the CPS wouldn't prosecute (because it's not actually illegal).