www.alphadictionary.com

Again today I read an article in the paper about a body found on the beach. Police said "There are no suspicious circumstances". But hang on, suspicious is clearly related to suspect. I suspect that Julie's party is really for her 50th birthday although she says it's just for fun. There is nothing sinister or criminal in my suspicion, but the police comment clearly implies that if it is suspicious, they believe it may well be sinister or criminal.

Where and when was 'suspicious' hijacked? I suspect it is classic Police euphemism. Just as the military sanitise the language for public consumption - collateral damage for civilian killings and so on.

Not so sure this was really 'hijacked'. Suspect seems always to have meant to look askance at, to mistrust. There are just varying degrees of mistrust involved, from simple doubt about the reasons for a party, to questioning someone's innocence of a crime.

Although an
online dictionary search offers this:
suspect
verb
/səˈspɛkt/

1.
have an idea or impression of the existence, presence, or truth of (something) without certain proof.
"if you suspect a gas leak, do not turn on an electric light"

2.
doubt the genuineness or truth of.
"a broker whose honesty he had no reason to suspect"