Parkin acted as one of several expert witnesses for the prosecution against William Edward Hickman, tried for the kidnap and murder of 12-year-old Marion Parker in December of 1927. Hickman was sentenced to death after a 13-day trial. He was executed at San Quentin, October 19, 1928.
A line of men and women, both seated and standing, wait within the Los Angeles Courthouse to witness judicial proceedings for William Edward Hickman, who confessed to kidnapping and murdering Marion Parker, aged 12. Hickman was tried and sentenced to death. He was executed at San Quentin, October 22, 1928.