A US lawyer has pointed out a huge legal issue surrounding the conviction of a mum found guilty of manslaughter after her son shot four children at school. Jennifer Crumbley is the first US parent convicted of manslaughter over a mass shooting carried out by her child, Ethan, who shot four people in a school shooting. Prosecutors accused her of being negligent in allowing her son to have a gun and ignoring warning signs. Her husband, James, is facing a separate trial on the same charges. Speaking to Jacob Rees-Mogg on GBN America, Jeff Swartz, a senior trial counsel in commercial litigation an…