Synthetic

In France, only the police are allowed to use drones and these are
being integrated into crowd control. They are coupled with synthetic DNA,
which is an invisible chemical marker (which becomes visible under
ultraviolet light). Plan is to spray Black Bloc individuals and 'see' where
they are dispersed in the crowd.

https://www.huffingtonpost.fr/2019/03/22/acte-xix-des-gilets-jaunes-ce-que-lutilisation-de-drones-dit-de-levolution-du-maintien-de-lordre_a_23698738/?utm_hp_ref=fr-homepage

https://www.liberation.fr/evenements-libe/2013/11/04/la-police-mise-sur-l-adn-synthetique_944437

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source: Le Monde