These three have a technological attribute — me — in common:
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What does each of these represent?
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How have these figured into actual criminology puzzles?
(No need to cite specific cases.)
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What am I?
No wordplay is afoot and
completeness includes a note about technologically historical context.
Thus,
“they are writing -
I am a sentence -
judges have to figure out criminal sentences”
would be discounted on account of incompleteness and wordplay.
(No encrypted data, by the way, just one low-contrast level of writing.)