suspect: not to be relied on or trusted; possibly dangerous or false :
"We are examining all parcels for possible bombs. A suspect package was received in today's mail...."
"His motives are suspect. We regard him as a psychopath, not to be trusted."
suspicous: having or showing a cautious distrust of someone or something :
"He's a known psychopath. I was suspicious of his motives from the start."
: causing one to have the idea or impression that something or someone is of questionable, dishonest, or dangerous character or condition :
"He disappeared under suspicious circumstances. Police suspect foul play."
• having the belief or impression that someone is involved in an illegal or dishonest activity :
"There was a foul odour emanating from his residence. Police were called when neighbours became suspicious. Police found six corpses...."