There has been a lot of discussion in our forums over the arrival of 'sus' in our current vernacular as well as its origin.
Inverse did some research for me to cut and paste:
The shortening of suspicious to "sus" first took place in England and Wales as far back as the 1930s as police jargon. Instead of using it as a descriptor, like "that person is sus," British cops would use the abbreviation to refer to the discovery of crucial evidence or information as having "sussed something out" or going on an investigation as "sussing out a situation or person."
The expression is still used colloquially today and is most commonly used to describe the action of discovering a secret, but it was a particularly oppressive policing practice that would drop the second S in "suss out."
"Sus law" was a nickname for a stop and search law enacted in 1824, that gained its monicker in the early-to-mid 1900s. It gave British law enforcement the power to search and potentially arrest people who they believed were up to no good. Specifically, the cops had to think a person was in violation of the Vagrancy Act of 1824, which only required them to establish that someone was a "suspected person" with intent to commit an arrestable offense.The practice was found to disproportionately target Black and brown people and have little-to-no impact on crime in London. This discrimination caused tension in communities all throughout England and was a major factor in what sparked the 1981 Brixton riot in London when thousands of protestors clashed with the Metropolitan Police.
No one is more suspicious than Sir Topham Hatt. That guy is up to no good.
