Grand jury is so named because traditionally it has greater number of jurors than trial jury, called a petit jury (from the French word petit meaning small).
Although mice tend to come out in the night when most of the occupants of the house are asleep or immobile. This allows them to stealthily infiltrate any of your food bags, crumbs etc. During the day time, mice will normally not come out, but if opportunities exist then they surely can.
For the past 2 years we have kept mouse traps open in the cars and have not caught mice in the cars. To check on this, we occasionally have forgotten to corral a car at night. and sure enough, in the morning we have a mouse or two in the traps.