Det Sgt Dollard, who interviewed Grey, told BBC Radio Cambridgeshire: "I'll always remember the morning after it occurred obtaining the CCTV and watching it in its entirety.
"In all honesty it's horrific and not appropriate for wider release to the public, but, if it were, then I think a lot of the arguments in relation to appropriate responses would be null and void."
He added that there were "considerations in relation to Auriol Grey's vulnerability" in their investigation.
"A lot of medical records... professional expert evidence was sought and presented to a jury, it's important to note, and with all that, in fact, she was found guilty of an unlawful act and that is why she was convicted," he said.
He said "what [Grey] did was wrong but ultimately that will not bring Celia back", and he did not believe her family "take any pleasure in the fact that a sentence was passed".
"I certainly urge people to think twice about commenting in relation to this case when they're not in possession of all the facts," the detective said.
"I've seen a number of ill-informed comments on various messaging sites as well and it's not helpful to anyone."
www.bbc.com/news/uk-england-cambridgeshire-64835197