Is it a lie not to volunteer information?

[bobzills]

Say you broke something (as an example, the other day when I got really steamed over the falling through of that missionary, I think kicked or slammed a cabinet door in my house, damaging it), is it a lie to not voluntarily admit to breaking it? In other words, say someone noticed the damage, but they merely say something, but they do not ask what caused it, and I go, “Okay”, basically acknowledging what they said.

Is this a lie? And, if so, is it a mortal sin/grave matter?

You have to admit that you broke the cabinet and you have to give restitution. Failing that it is a sin, which could be mortal if the amount of damage is large, say about one day’s pay.