Somewhat illogically, the English word “suspicious” can be used to describe both the act of being distrustful (such as the proverbial girlfriend’s father) as well as the condition of being questionable (like the proverbial lack of noise from the kids’ bedroom). In the German language, these are separated:

– “misstrauisch” is used to describe people who are wary and distrustful (e.g. the old lady next door, peeking from behind her curtains):

“Die fehlenden Kekse machen mich misstrauisch.” – “The missing cookies are making me suspicious.”

– “verdächtig” refers to people or situations that are dubious, suspect, fishy or dodgy (e.g. a flag waving in the wind on the ‘moon’, to some people):

“Es ist verdächtig still.” – “It is suspiciously quiet.”
“Das ist sehr verdächtiges Verhalten.” – “That’s very suspicious behavior.”

Another word for “suspicious” is “suspekt”:

“Er war mir von Anfang an suspekt.” – “I was suspicious of him from the very beginning.” / “He was suspicious to me from the very beginning.”