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.
Mouse Behavior. Mice are nocturnal creatures, and, therefore, are rarely seen by the homeowner. The most obvious indicators of their presence are droppings (1/8 - 1/2-inches long, dark and pointed at both ends), sounds of them running, gnawing or squeaking, or damage to stored food or materials used for nesting.