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.
It's not cruel to let them out at night, but it is highly dangerous. A car could not see them as easily, and hit them. It could eat something and get poisoned. A night creature could attack them. It could not see a ditch or something like that, fall in and not be able to get out.f you live near a busy road or in a dangerous area for animals i would keep it inside. However if you cat loves to be outside at night and you live in a safe area, then no, it's not cruel :) Hope I helped xx. Source(s): Personal Experience.