3 On 25 November 1997, as was the usual practice for fishermen early in the season, the respondent had been fishing in shallow water where almost all of the rock lobsters were close to the minimum size. Having returned to port he took three crates to the factory at Lancelin. They contained a total of between 180 and 200 rock lobsters which had been taken from 101 pots pulled that day. Cameron Dawe-Smith, the duty fisheries officer at the factory, examined the fish and measured them with a Sheridan gauge, an almost rectangular, flat piece of pressed metal on one side of which is a gap not less than 77 mm long. After deciding that 28 were undersized he summoned Robert Sutton, a senior fisheries officer. Mr Sutton checked some of the fish himself and confirmed that they were undersized. By then the respondent had been told of the problem. He went to the factory, measured the 28 fish and agreed that they were all undersized. The officers seized them and, accompanied by the respondent, took them to the district office at Lancelin. There Mr Dawe-Smith interviewed the respondent. Then he measured the 28 fish with Vernier callipers, scientific instruments which are well recognised. Mr Sutton verified the readings on the callipers but did not do the actual measuring. In respect of each fish the officers concluded that its carapace was of less than the minimum length of 77 mm. In one case the measurement was 76.90 mm - that is, within the tolerance margin of .20 mm allowed as a matter of policy - and so the respondent was charged in respect of only 27 fish. Neither the respondent nor, to his knowledge, Mr Lee-Wilson had previously been prosecuted for a fisheries offence.