Heron, Denis Caulfield (1824–81), lawyer and politician, was born 16 February 1824 in Dublin, eldest son of William Heron, esq., of Newry, Co. Down, and his wife Mary, daughter of Thomas Maguire, merchant, of Enniskillen, Co. Fermanagh. He was educated at Downside School, near Bath, and at TCD. In 1843, three years into his degree, he was eligible in terms of merit for a scholarship, but was refused as a catholic. Through application to the queen's bench, he forced the university to hear his case, represented by the catholic barristers D. R. Pigot (qv) and Stephen Woulfe Flanagan (1817–91), on 11–12 December 1845. The case was dismissed but proved sufficiently embarrassing to prompt the college to endow some non-foundation scholarships for catholics. Heron proceeded to enjoy a successful university career, graduating BA (1845) with a gold medal for classics, and being elected auditor of the College Historical Society in 1846. The following year he published The constitutional history of the University of Dublin, in which he demanded college reform regarding the position of catholics. After attendance at the King's Inns (1843) and Lincoln's Inn (1845), he was called to the bar (1848), but first embarked on an academic career. Though unsuccessful in his application for the Whately chair of political economy in TCD, he was appointed Barrington lecturer in 1849; the same year, he received a more permanent position in the form of the professorship of jurisprudence and political economy at the newly established QCG. In this capacity he formulated the new syllabus, took on the duties of dean, and acted as university examiner 1852–4. The absence of suitable texts prompted him to publish An introduction to the history of jurisprudence (1860). A section of this was later published as a separate volume, The principles of jurisprudence (1873), in which he propounded common Victorian beliefs concerning natural law and morality. The legal historian Liam O'Malley has termed these works wide-ranging but badly organised. In the field of economics Heron was chiefly interested in land and taxation issues. A founding member of the Dublin Statistical Society, he served on its council (1850) and contributed a number of papers between 1851 and 1872. His 1862 paper ‘Historical statistics of Ireland’, in which he sharply criticised emigration levels and blamed economic decline on defects in the land system, aroused great controversy and has been described by Mary Daly as ‘a precise summary of what was to become the nationalist interpretation of Irish economic history’ (Daly, 41).
In 1859 he resigned his chair in order to return to the bar, where he quickly developed a large practice on the Munster circuit, mainly as a commercial lawyer and in the bankruptcy courts. He took silk in 1860 and was law adviser at Dublin castle for two months (April–July 1866). A staunch nationalist, he defended a number of the 1867 Fenians and succeeded in securing a few acquittals. His most celebrated case was the trial of the Fenian crew of the Erin's hope, a ship that brought munitions from New York to Sligo in May 1867. Heron's defence hinged on the fact that his clients were naturalised Americans – an application that proved unsuccessful but drew both media coverage and attention from the American government, resulting in an 1870 act allowing a British-born subject to divest himself of his birth allegiance and adopt another citizenship. This portfolio, together with clerical support, made Heron a strong liberal candidate for Tipperary in the 1869 by-election. However, he was up against the Fenian prisoner Jeremiah O'Donovan Rossa (qv), who was elected as an independent nationalist in protest at the government's refusal to grant political prisoners amnesty. As a convicted felon, Rossa was disqualified; at a second by-election the following year, Heron defeated the Fenian Charles Kickham (qv) by four votes, to be returned for Tipperary (1870–74). In parliament he supported the 1870 land act and that year proposed a land bill of his own. Generally he confined himself to Irish questions, though he did champion women's franchise in 1872 and 1873. As a parliamentary speaker he was neither frequent nor forceful, and he did not seek reelection, preferring to concentrate on his legal career. He was elected a bencher of the King's Inns in 1872 and appointed third serjeant-at-law on 25 October 1880 in Gladstone's second administration. A counsel for the crown during the Parnell state trial in December 1880, he was a definite candidate for the judicial bench until his career was cut short by his premature death on 15 April 1881, when he collapsed while salmon fishing on the River Corrib in Galway. He was buried in Glasnevin cemetery.
He married (1854) Emily, sister of Judge John David Fitzgerald (qv). They settled at 7 Upper Fitzwilliam St., Dublin, but nine years into the marriage she died on board the Holyhead ferry as it approached Kingstown (Dún Laoghaire) in 1863. There were no children.