Same rule I give my witnesses. "Always tell the truth"
I was in a situation early in my career where the truth wasn't the right answer in this sort of situation and I learned that, instead, whenever in doubt, a lawyer should just accept sole responsibility.
I was a first year public defender. I appeared almost exclsusively in front of the same two judges. It was just misdemeanor stuff and I probably averaged a trial per week (and, as a result, I got phenomenal trial experience working cases that I really couldn't screw up too much) and at any given time I had a couple of dozen set. Naturally, it was very common for trials to get continued for witness availiability issues, over-setting, or because settlement seemed likely. It was therefore common practice to informally communicate with court clerks and the state on the day of trial to figure out if a trial was actually going. It was then commonplace for us to rely on these informal conversations when releasing witnesses or telling defendants not to appear (we'd get a formal order setting the new date shortly therafter).
In one particular trial I had filed a motion to continue a day or two in advance because, IIRC, I had a witness availability issue. I had reached out to the prosecutor who indicated he opposed. I put his opposition on my motion. We didn't receive a ruling. The trial was set in the afternoon and both the prosecutor and I had witnesses driving multiple hours to attend. That morning, with consent from the prosecutor, I called the court to inquire about the motion. The conversation went like this.
Me: Good morning, it's [Woz] and I'm calling about the X case set for trial this afternoon. I had filed..
Clerk: Continued.
Me: The judge granted my motion to continue? Are you...
Clerk: Yep. Continued.
Me: Okay. Thanks.
I call the prosecutor and informally tell him. He releases his witnesses and I release mine. However, we don't get the order to continue so we're confused. We both still had to be at court for other matters so we go into the court hearing as scheduled. Judge takes the bench and, to our surprise, asks if we're ready to proceed. Prosecutor, who is in a tough spot, has to say no and that he released his witness from his subpoena. Judge obviously asks why. At that point I stand to answer for the prosecutor and explain that the prosecutor reasonably relied on my say so that the matter was continued. I further explain that I had called the court and was advised it was continued. We then have this exchange:
Judge: The state objected. Why would I have then granted the continuance?
Me: (stammering) Judge, I don't know, but I called and identified the case and the clerk said it was continued...
Judge: I know you called. I spoke to my clerk and she says she specifically told you it was not continued. Are you calling her a liar?
Me: Well, no, but she said...
Judge: Did you mishear her?
Prosecutor (whispering to me): Just say you misheard...
Me: Judge I swore an oath to tell the truth and she said continued and I even asked twice..
Judge (interrupting): My clerk wouldn't lie to me. And, unfortunately, because of your actions I now have no choice but to continue this case.
The judge then proceeds to pick a date he knows I was out of the office. It's been eleven years since it happened and, while I have done a lot to repair the damage caused I am pretty sure the judge still holds that incident somewhat against me. I would have been for better off just conceding that I may have misheard the clerk, taking the blame, and not insisting on the truth if the truth didn't get me anywhere with the judge.