Eyes still flicking now and then back to Albus, Severus takes the paper and writes, "I must tell you that evidence of the sort you speak of can be manufactured. There are a number of spells and, I regret," he adds grimly, looking closer to his proper age, "draughts affecting the mind and will, only one of which is illegal, which can be used both to influence behavior and to induce false confessions. Be wary of expressions of enmity springing from motives which don't hold up, or which do but are not of long duration."
He stares grey-faced at Holmes's final question for a while, as the question of beverages is dealt with, an absent, "Tea, please, for me," escaping him. Finally, he sets down his pen with a decided click, shoves the paper away, takes a more respectable swallow of his brandy, and devotes himself and a wicked little copper knife to meticulously eating every scrap of flesh off the apple core.