I don't think Wallace had the time to commit the murder, nor do I think he had any motive to do so. By all accounts, he and his wife were quietly content.
According to Thomas Slemen in "Murder on Merseyside" (Hale 1994), the houses in that street were all built at the same time, by a single builder, who imprudently used a single model of lock for all the doors. Mr. Slemen's source relates that he discovered this when he came home tipsy one night, and unlocked and entered the wrong house. Furthermore, Slemen reports that prior to the murder, there had been an outbreak of burglaries on the street.