Collocations for suspicious - adj.

be, feel, look, seem, sound
become, get, grow
I think they're starting to get suspicious.

remain
make sb
Something about her smile made him suspicious.

extremely, fairly, very, etc.
deeply, highly, particularly
She remained deeply suspicious of computers.

increasingly
a little, slightly, etc.
His voice grew slightly suspicious.

immediately, instantly
naturally
I have a naturally suspicious mind.

rightly
Voters are rightly suspicious of attempts to save money in the area of education.

overly

about
They were somewhat suspicious about her past.

of
She was highly suspicious of his motives.

be right to be suspicious (of sb/sth), have reason to be suspicious (of sb/sth)
have a right to be suspicious (of sb/sth)
Parents have every right to be suspicious of what the experts tell them.

be, look, seem, sound
We have to carry on as usual or it would look suspicious.

consider sth, find sth, regard sth as, treat sth as
I find it very suspicious that he left halfway through the morning.
Police are treating both fires as suspicious.

extremely, fairly, very, etc.
highly
He was seen acting in a highly suspicious manner.

a little, slightly, etc.

hear anything suspicious, see anything suspicious
Inform the police immediately if you see anything suspicious.

Suspicious is used with these nouns:
activity, behaviour, character, circumstance, death, eye, glance, look, manner, package, transaction