Portland's topline Robert Tulloch and Clive Clarke refused to continue batting at 21 for two in the second innings after both were struck a number of times by the ball on what was described as a deteriorating wicket.
Final scores were: St. Catherine 157 for seven declared (Keith Hibbert 47 not out); Portland 81 (Oneil Richards three for 14, Audley Sanson three for 23) and 21 for two.
As a result of obtaining maximum six points for an outright win, St. Catherine have joined Melbourne in the lead with 17 points.
Points standings after five rounds are as follows: Melbourne and St. Catherine 17 points each from five matches, Lucas and Kensington 16 each also from five matches, followed by Kingston 15 but from four matches, Portland 10 also from four, Police 9 points from four matches, JDF 9 from five matches, Boys' Town 5, Tivoli 4 and St. Thomas 1. Police drew a bye over the weekend.