Stewart was identified after sharing an image of a block of cheese in the palm of his hand, from which his fingerprints were analysed.
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Sorry. Not buying this explanation, especially if that is the photo, which is rather low-res. In fact most social media sites automatically reduce the resolution of any photos uploaded because they know people are likely viewing the photos on a small screen, such as their phone, and not on a large monitor.
Phones have incredibly hi res cameras
The photo as posted here (and in the OP article) is at least a few generations/copies/reductions after the original, and appears to have been blurred, probably specifically to obscure the fingerprints. We don't know what the original looked like, but it was almost certainly better than the copy we're looking at here.
That said, the fingerprint identity verifier on modern smartphones doesn't need very much to go on. I'm sure a government computer exists that can extract information from a low-res photo fairly accurately.