In 1876 and 1877 McParland was the star witness for the prosecution of John Kehoe and the Molly Maguires. Twenty members were found guilty of murder and were executed. This included Kehoe, a former union leader who was convicted of a murder that had taken place fourteen years previously.
There was a great deal of controversy about about the way the trial was conducted. Irish Catholics were excluded from the juries while Protestant immigrants from Germany who could not speak English were accepted. Welsh immigrants, who had for a long-time been in conflict with the Irish in Schuylkill County.
Most of the witnesses who provided evidence in these cases were like McParland on the payroll of the railroad and mining companies who were attempting to destroy the trade union movement. In other cases, defendants were