Netflix - The Staircase...innocent or guilty?

[CoRhona]

YABU - it was an unfortunate fall

YANBU - guilty as sin

(If you've not watched it but plan to, read up more about it afterwards...I was )

I was intrigued by the total lack of mention of the huge stairlift, with the chair part pictured at the bottom of the stairs in the crime scene photos. Surely falling against that would have caused lacerations?