Porter, Sir Andrew Marshall (1837–1919), judge, was born 27 June 1837 in Belfast, eldest son of the Rev. John Scott Porter (qv) of Belfast, unitarian minister, and his wife Margaret of Belfast, daughter of Andrew Marshall, Royal Navy surgeon. He was educated at the Royal Belfast Academical Institution and matriculated for QCB (1853), where he graduated BA (1856). Deciding on a legal career he was admitted to the Middle Temple, London, in Hilary term 1857 and then to the King's Inns, Dublin, in Hilary term 1859. He was called to the Irish bar in Trinity term 1860 and initially practised on the north-east circuit. While somewhat reserved, he was an able orator and possessed a comprehensive knowledge of company law. He soon had a thriving practice, and in 1861 was appointed Barrington lecturer on political economy at Queen's. In 1872 he was made a QC, and in 1878 became a bencher at the King's Inns.
A confirmed Liberal, he was a staunch supporter of W. E. Gladstone and described his land act of 1881 as the ‘greatest boon ever conferred on Ireland’ (Stenton, 315). He was also in favour of reform of the grand jury laws, and in November 1881 was appointed solicitor general for Ireland. In the Londonderry by-election of December 1881 he was elected as a Liberal MP and distinguished himself in debates on Irish affairs in the commons. In 1882 Gladstone offered him the Irish chief secretaryship but, not interested in making politics his lifelong career, he refused. Appointed attorney general for Ireland in 1883, he successfully prosecuted the Phoenix Park assassins in the trial of April of that year. He was not satisfied, however, with the evidence that the police had obtained from informers, and had the date of the trial put back while he checked certain facts himself.
In December 1883 he was raised to the bench as master of the rolls (1883–1906), resigning his parliamentary seat, and was sworn of the privy council. While he had previously specialised in company and common law, his career as a chancery judge was distinguished and, showing little tolerance for barristers who tried to waste court time with pointless orations, he became renowned for the brevity and precision of his judgements. Few of his judicial decisions were ever successfully appealed. Created a baronet in 1902, he retired in 1906. During the course of his career he was awarded an honorary LLD from QCB (1882) and also an honorary LLD from TCD (1889). He died in Dublin, 9 January 1919. His Dublin residences were at 42 Merrion Square East, and at Donnycarney House.
He married (12 April 1869) Agnes Adinston Horsburgh, daughter of Lt-col. Alexander Horsburgh of Horsburgh, Peebleshire; they had four sons and two daughters. His eldest son, John Scott Porter (b. 1871), succeeded to the baronetcy. His third son, Andrew Marshall Porter (qv), played hockey for Ireland and died in action during the second Boer war while serving with the Imperial Yeomanry.