The Murder of Mavis Nelson

Becker's prior felony conviction was for second-degree manslaughter in the 2015 death of his four-month-old son in Pullman, Washington. The infant was found asphyxiated after choking on a plastic garment bag; the death was ruled accidental. Becker was convicted in 2016 and sentenced to 27 months, the maximum available given the absence of prior felony convictions at that time. That conviction placed his DNA and fingerprints in state and federal databases, which proved decisive in the Nelson investigation. The nature of the prior offense, the death of a dependent in his care, is documented in the record but does not constitute a pattern of predatory sexual violence in the public record prior to Nelson's murder.

Becker and Nelson were known to each other prior to her death. Investigators noted they may have worked at the same transitional housing facility at some point and shared common acquaintances within the social services community in Seattle. Becker lived approximately two blocks from Nelson's apartment. On the night of her death, Nelson reached out to him after a domestic violence incident involving another man, which Nelson's sister believes may have been a request for support. This access pattern, a familiar contact reached in a moment of vulnerability rather than a stranger encounter, is consistent with the majority of femicide cases in which victim and offender have a prior social connection.

Becker told investigators that Nelson's body was stored in his bedroom closet for approximately one month following her death, and that he and at least one other person engaged in sexual acts with her remains during that period. The charge of sexually violating human remains, to which Becker pleaded guilty, reflects this conduct. Post-mortem sexual violation is rare in homicide cases and is classified in behavioral literature as a distinct paraphilia; it is associated with offenders who seek absolute control over a victim and for whom the death of the victim does not extinguish the sexual motivation. Its presence as a charged and admitted element of this case was a significant factor in the sentencing outcome and in the possibility of a review board imposing additional punishment.

Nelson's remains were dismembered before disposal. Becker told investigators he assisted in the dismemberment but claimed another person carried it out. Investigators stated at the time of charging that evidence did not corroborate the involvement of a second person in the killing itself, though charging papers noted that one or more other individuals may have been involved in the disposal. Nelson's remains were thrown from an elevated roadway onto the Burke-Gilman Trail below; surveillance footage captured two figures at the disposal site. The selection of a public trail near a university campus as a disposal site, combined with the extended retention of the body prior to disposal, reflects a high-risk post-offense behavioral pattern inconsistent with careful planning.

Mavis Nelson was an Indigenous woman living alone in an urban environment and working in social services, a profession that brought her into contact with people in precarious circumstances. Indigenous women in Washington state are reported missing and murdered at approximately four times the rate of white women. At the time of Nelson's death, Seattle led the nation in documented cases of missing and murdered Indigenous women and people. Nelson's family initially had little confidence her killer would be identified, a reflection of documented historical patterns in which cases involving Indigenous victims receive less sustained investigative attention. The outcome in this case, including a guilty plea and 34-year sentence, was described by advocates as a remarkable and relatively rare result.

The investigation succeeded through the convergence of multiple evidentiary threads: cellphone records identifying a recurring contact number that went silent after Nelson's disappearance; fingerprint evidence from beer cans in her apartment; DNA recovered from gloves at the disposal site; and a CODIS database hit linking all physical evidence to a named individual. Detective Rurey's decision to obtain a search warrant for the phone number, rather than accepting that the Auburn boyfriend was the last contact, was the pivotal investigative step. Becker's nine-hour interrogation provided additional corroborating detail. The case demonstrates the forensic value of maintaining prior offender DNA in national databases and the investigative importance of cellphone record analysis in cases where the victim's last movements are otherwise unclear.