Knife crime and offensive weapon convictions and cautions fall â but selected serious cases involving blade and sharp instrument rise A man holding a knife behind his back THE number of knife crime and offensive weapon convictions and cautions went down in Greater Manchester for the first time in four years – but the amount of a select group of serious crimes with a blade increased. Data released by the Ministry of Justice shows that there were 755 convictions or cautions in the region in the year up to June 2016 in crimes involving a knife or sharp instrument. This figure increased that month in 2017 (843), 2018 (989) and 2019 (1,145).