The Australian white supremacist who murdered 51 Muslim worshippers at two mosques in Christchurch in 2019 has been prevented from appealing against his guilty pleas, after one of New Zealand’s highest courts said his bid was “utterly devoid of merit”. Brenton Tarrant, who is responsible for the worst mass shooting in New Zealand’s history, asked the court of appeal in February to allow him to appeal against his guilty pleas, claiming harsh prison conditions had affected his mental health and compelled him to admit to the crimes. In a decision released on Thursday, the court said it did not accept Tarrant’s evidence about his mental state, which was inconsistent with detailed observations of prison authorities, mental health professionals and trial lawyers.…