Prior to 1790, Pennsylvania felony offenses were tried by Supreme Court judges who traveled throughout the state in the spring and fall for that specific purpose. The Pennsylvania Constitution of 1790 removed sole authority for these cases from the Supreme Court and instead ordered that a Court of Oyer and Terminer and General Goal [sic] Delivery be established in each county. Unlike the Court of Quarter Sessions, the Court of Oyer and Terminer tried capital offenses including murder, treason and arson. Both of these courts were abolished in 1968 when these functions were incorporated into the Court of Common Pleas.
While a modern review of the oyer and terminer records may be interesting, individual tastes will dictate the level of pleasure at finding one's ancestor among these records. They do, after all, contain some of our more infamous Pennsylvania residents.
Certainly one of the most well-known cases tried in the Court of Oyer and Terminer would be that of the Molly Maguires. A renegade group of Irish-Catholic miners, the Molly Maguires are either ground-breaking labor advocates or ruthless murderers, depending on who is telling the story. Either way, their trials and subsequent executions in Carbon and Schuylkill Counties are forever recorded in the annals of history via the Court of Oyer and Terminer.
If the idea of finding a "black sheep" grazing in your family tree is appealing, include oyer and terminer records in your research plan. Check individual county court houses, and historical and genealogical societies to learn if their archives include these records. A sampling of what can be found at the state level is listed below. Some of these records may be online, so remember to search the internet as well:
State Archives -
Berks County, indictments, 1780-1899
Carbon County, minutes and trail summaries, 1872, 1876-1878
Chester County, dockets and index, 1802-1935
Fayette County, dockets, 1920-1964
Indiana County, papers, 1900-1910
Lehigh County, papers, 1873-1910
Perry County, docket "A" to trial docket, 1914
Somerset County, dockets, 1855-1899
Union County, dockets, 1896-1956
Court Papers of the Courts of Oyer and Terminer, 1757-1761, 1763, 1765-76, 1778-82, 1786-87 (documents from the first nine PA counties)
State Library -
Records of the Courts of Chester County, Pennsylvania, 1681-1697
Kulp's Luzerne Legal Register Reports, 1895-1904
Dockets of the Court of Oyer and Terminer of Pennsylvania, 1778-1827
American Trial Court Record Series III, 1957