For example, "Mom, there's a candy wrapper under (my brother)'s bed!" is a true statement, but the pure truth is "Mom, I ate a candy without permission and put the wrapper under (my brother)'s bed so he would be blamed for the missing candy!"
I am attempting to convey a lie by telling a truth and omitting details that would give context to that truth.
I believe you are referring to "whole truths," which yes we teach to children and swear on the stand in court. A "pure" truth carries different connotation here I think, and is not said in general.
Since GP might not have English as their first language (their post points out that they are European) I assumed the choice of "pure" was a translation of their language's equivalent to "whole" and therefore being treated as equivalent.
For example, "Mom, there's a candy wrapper under (my brother)'s bed!" is a true statement, but the pure truth is "Mom, I ate a candy without permission and put the wrapper under (my brother)'s bed so he would be blamed for the missing candy!"
I am attempting to convey a lie by telling a truth and omitting details that would give context to that truth.