If we want to say "I gave the knife to the officer", we say {yaSvaD taj vInob}.

Can someone please explain, why it would be wrong to say {yaSDaq taj vInob} ?

You use -Daq when you're specifying a location and -vaD when you're specifying a beneficiary or recipient.

yaSDaq taj vInob means I give the knife (to someone unspecified) at the location of the officer.

-- 
SuStel
http://trimboli.name