Things which are done simultaneously with an act are supposed to be inherent in it; to be a constituent part of it.

Explanation

(English-origin maxim.) Contemporaneous acts and declarations made at the time of a transaction are admissible as part of the res gestae — they are woven into the act itself and inseparable from it.

Where this applies

• At the moment a seller hands over the keys to a house, he tells the buyer 'the basement floods every spring' — that statement is part of the transaction itself and admissible as evidence.
• During the signing of a partnership agreement, one partner says 'this only covers the Texas operations,' and that contemporaneous declaration is treated as part of the deal.
• A witness hears a landlord say 'I'm raising rent because I don't want kids in the building' at the exact moment he hands the tenant a new lease — that statement is inseparable from the act.