This is a "none-of-the-above" problem. My grandson's mom, by dau-in-law, is having a LOT of problems. My son is SEVERELY critical of her in from of the 9 y/o, particularly accusing her (second-hand) of lying, and she may very well be lying. BUT, how do I convince my son it's HURTING HIM AND his SON. My son says he wants the boy to know lying is "wrong." But not this approach! Can anyone give me some words to show my son this is NOT the way?

how wonderful that you are able to divide our loyalty foryou own child and think of the welfare of your grandson... your grandson and daughter in law are luck to have you as you obviously 'do whats right'.

Your son is not teaching his son about lying , but he is teaching his son how to be little and judge others, huniliate and control .. I would advise him to find himself a friend his own age that he can confide in and 'bitch' about his 'ex's lies, teaching a child not to trust his mothers words will severely effect the 9 year old ... I personally would die of shame if someone pointed out that I was a liar in front of my child ... errrm!! did I admit to lying...ooops!! or is it fibbing or is it keeping my business mine... if your daughter in law keeps things from your son..is it because it is non of his business..perhaps if that is so you could point that fact out to him. Maybe as a mother you could point out a few of your sons fibbs (in private ) and ask him if you should share his fibs (extention of truths..whatever) with you grandchild in order to help out with the teachings...(don't of course) but it may help get him get over his attitude .... the old 'he who lives in glass houses should not throw stones'.
Anyway good luck and i wish there were more Grandmas out there to look after the interests of the kids.

I can somewhat identify with your situation. I used to scold my child in front of my parents and my own mother would say, "Don't be so hard on him" or something like that right in front of my child. We went through months of my disciplining with my son going behind my back to my mother and her taking away his punishment because of it. Finally, I said to her in a very stern voice, "Don't do that to me in front of my child! I am his mother!" My dad actually took my side in front of my child and my son witnessed the entire event. I informed her in front of my son that my role was his mother and her role was the grandmother, so she was a step away. I was the immediate parent. In your case, it's both immediate parents, so it's also a difficult one. I'd suggest that you suggest (in a non-threatening way) that your son excuse himself and his wife and talk to her in private of his disapproval of her "lying". Kids, even grown ones with kids of their own, do not like to be corrected by their parents, so be sure you suggest this to your son in a more conversational tone rather than a parental one. And little ones shouldn't be present when the parents have disagreements. Explain to your son that when he scold your daughter-in-law in front of their child that he is acting childish by having to have an audience and "name-calling". He ought to respect that if he truly does want to be a good, mature parent. Good luck to you!