Minister Xing had absolute trust in Xiao Liulang, first because Xiao Liulang was just a frail scholar who, facing a vicious criminal, could not ever possibly commit murder to silence someone, and second, because Xiao Liulang had always made an impression as someone who avoided worldly affairs and was incorruptible and upright.
Nobody could fabricate evidence, but Xiao Liulang would not!
Far from worrying that Xiao Liulang might falsify anything, Minister Xing was more concerned that Xiao Liulang, seeing a living person die before his eyes, might feel compunction and be left with a shadow over his investigation.
Minister Xing did not recall in the slightest that Xiao Hen had once worked as a coroner; having dissected corpses, was he going to be scared by a living person dying?