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.
The period during which the female is receptive to the male and allows breeding is about 12 hours and usually occurs at night. Female mice can come back into heat within l4-28 hours after giving birth to a litter.