[glorfindel]

It would be unethical for the defense attorney, having accepted the job , not to provide the best defense possible. Although he thinks the best defense is for his client to accept the plea bargain, if his client refuses, he must attempt, to the best of his legal ability, to gain acquital. This is why defense attorneys often gain acquitals based on legal "technicalities," although they're certain their client is guilty.

The defense attorney cannot "get into trouble" over what his client says under oath. He's not the one committing perjury.