Just recently I met up with a police officer who had been involved in the original murder investigation and matricide transference (displaced matricide) was mentioned. This has always been my opinion since the confession in July 2013.
"Sexual killing is the intentional killing of a person during which there is sexual by the perpetrator (before, during, after or throughout the act). In the recent century different terms were used in order to refer to sexual homicide: lust murder (Krafft?Ebing, 1886; Hazelwood, 2001), sadistic lust murder (De River, 1958), sadistic murder (Douglas et al, 1992), lust killing (Malmquist, 1996), sex murder (MacDonald, 1986), erotophonophilia (Money, 1990), sexual murder (Grubin, 1994), sexual homicide (Ressler, Burgess & Douglas, 1988).