DNA Explainer: Why experts are seeking pardon for âAustraliaâs worst female serial killerâ The experts maintain that Folbigg deserves pardon as a recent study showed that her victims may have died due to natural causes. Share Updated: Mar 9, 2021, 01:53 PM IST Several scientists and experts are urging the Australian government to pardon convicted child killer Kathleen Folbigg, who is regarded as the country's worst female serial killer. The experts maintain that Folbigg deserves pardon as a recent study showed that her victims may have died due to natural causes. It is to be noted that Folbigg's victims were four of her children. She was convicted in 2003 for killing her children as infants between 1990 and 1999.