I recently had to answer a question about lying I thought about it and this is what I think about it. I believe that if you tell even one lie you are a liar does this mean you tell lies all the time no. When you tell a lie you are a liar where most people make the mistake is in mixing up a liar with a chronic liar. A chronic liar is someone who for whatever reason either cannot or will not tell the truth. Nevertheless, keep in mind there are times when it is necessary to tell a lie in order to save some one or to protect someone or something. This does not make it not wrong just the lesser of two evils.
Lying is lying no matter what.
Lying to cover for someone who did wrong is harmful for both you and the one who did wrong. It is harmful for them because you are condoning their behavior and in a way encouraging them by allowing them to escape the consequences of their actions. It is harmful for you personally because you know what they did and you know they will likely do it agene making you as responsible for what happens as they are.
Lying or omitting certain details to protect the innocent or elderly from harm is still lying but in this case it is necessary. Sometimes it is more harmful and unnecessary for someone to know what someone they loved did especially if that person is no longer alive. It is better for them to remember them as they believed them to be than for them to know and to know there was nothing they could have done to change things.