It is always the responsibility of the older person to make sure the person they are with is legally able to consent. This is intentional. The law is designed to protect young people and to prevent adults who cause harm from using excuses to avoid accountability.
If someone genuinely tried to confirm another person’s age and was lied to, the legal system exists to examine all the facts. Everyone is presumed innocent until proven guilty, and courts consider evidence, intent, and circumstances before reaching conclusions.
At the same time, age of consent laws are written to be strict because individuals who intend to exploit minors may attempt to manipulate situations or claim they were misled. This balance helps ensure protection for young people while allowing the legal system to fairly assess each case.