The Mass State Statute does not provide for a defendant charged with first-degree murder to enter a guilty plea-- partially explaining BW's partial change of plea on only two counts. Also, a conviction of first-degree murder comes with an automatic appeal, where not even a conviction at trial will be final.
IMO, it's more likely that BW will never proceed to trial on Dec 1, and is probably in the negotiation phase with prosecutors right now, seeking to plead guilty to a lower charge of 2nd degree murder or manslaughter, where BW's objective is to preserve his rights to parole.
The Norfolk County DA's office is so compromised right now by its investigators and its leader that I don't know how they don't make a deal with Walshe for 2nd degree murder to ensure justice for Ana. JMO