whoever that person is, whether he is your best friend or someone else, you should not easily believe what he says. because you surely know that someone is not always good, and someone is not always bad. even though he is your best friend. maybe one day he betrayed you. You will never know what will happen in the future, and what is on his mind.
Even if he is a friend, or someone else, you must also remain vigilant. You also don't deserve to easily trust him. remember the crime occurred not because there is an intention of the perpetrator. but because there is a chance. so whoever that person is, you must remain vigilant.