Not to be negative, but to at least consider another viable viewpoint: So you have a witness who used to work for the defendant. If I am the defendants lawyer, I paint this ex employee witness as an unhappy employee. It’s what my company has done in lawsuits against us. Yep, you paint the picture that he is a disgruntled employee trying to seek revenge for the wrongs he feels the company did to him. Once you paint that picture, you have invalidated his testimony. Not that I am a lawyer, but I do watch a lot of Perry Mason and I slept in a Holiday Inn