 McConnell 's work mainly focused on poison and blood analysis , and she testified in many criminal cases as an expert witness . Her work often involved determining the cause of death when poisoning was suspected . In 1930 , she investigated the death of a ten @-@ year @-@ old Denver girl ; the case was referred to at the time as the city 's " most famous and controversial murder case " . Although she initially suspected the girl had been poisoned , McConnell discovered crushed glass in the girl 's stomach and blood stains in the family car ; her testimony led to the sentencing of the girl 's stepmother for murder . In 1936 , McConnell testified against suspected rapist and murderer Joe Arridy after finding fibers from the bedspread at the murder scene under the suspect 's fingernails . ( Although Arridy was convicted of murder and executed in 1939 , he was granted a posthumous pardon in 2011 . ) McConnell also discovered that murder victim Georg Obendoerfer had been killed with a lethal dose of arsenic , which led to further investigations confirming that Anna Marie Hahn had killed Obendoerfer , as well as other men in the same way . McConnell testified at Hahn 's trial in Cincinnati and Hahn was subsequently convicted and executed . After she was called to Raton , New Mexico as a key witness in a murder trial in 1935 , a court reporter for the Raton Range wrote that McConnell " has gained a national reputation ... in her blood analysis work " . Additionally , she is thought to be the United States ' first female forensic pathologist . Despite working on numerous high @-@ profile , widely publicized cases , McConnell kept her life as private as possible and only ever gave one interview during her career . 
