Another argument that occurs to me:
Imagine if it was the norm among criminal defense lawyers to hold back when they believe their clients are guilty, and to advocate zealously when they believe they’re innocent. Now, imagine a lawyer who mostly follows this practice, but engages in a bit of corruption: pay enough, and they’ll act like you’re innocent even when you’re not, or at least there’s a chance they will. Of course, they do this rarely enough that the prosecutors won’t notice. The prosecutors, in turn, see the corrupt lawyer not holding back, and take this as reason to believe the client is likely innocent; at this point, perhaps their code of ethics kicks in, and they less-than-zealously prosecute the client!
Another argument that occurs to me: Imagine if it was the norm among criminal defense lawyers to hold back when they believe their clients are guilty, and to advocate zealously when they believe they’re innocent. Now, imagine a lawyer who mostly follows this practice, but engages in a bit of corruption: pay enough, and they’ll act like you’re innocent even when you’re not, or at least there’s a chance they will. Of course, they do this rarely enough that the prosecutors won’t notice. The prosecutors, in turn, see the corrupt lawyer not holding back, and take this as reason to believe the client is likely innocent; at this point, perhaps their code of ethics kicks in, and they less-than-zealously prosecute the client!