Judge Tammy Kemp took the rare step of sequestering the jury, shielding them from outside influence and local news coverage. Photograph: Tom Fox/APThe judge in the murder trial of a former Dallas police officer charged with shooting and killing a black neighbor has taken the rare step of sequestering the jury.Former officer Amber Guyger, who is white, has told investigators in Texas she mistook Botham Jean, 26, for an intruder after she mistakenly entered his central Dallas apartment one floor above hers.The shooting in September last year, one of a series of high-profile killings of unarmed black men and teens...