Edward Targowski QC said Kimberley Hainey, a heroin addict and alcoholic with a history of mental health problems, could not be held responsible for the death of her son Declan.
The toddler was found dead in his litter-filled cot in the rubbish-strewn home he shared with his mother in Paisley in March 2010.
He had not been seen alive for months and experts who examined his body believe he may have lain dead for at least eight months when he was found.
Numerous friends, neighbours and relatives have told a Fatal Accident Inquiry (FAI), which is currently ongoing to try and establish how Declan died, they saw Kimberley alone on various occasions when she said that he was being looked after by her mum, Elizabeth Rodden.
But Mrs Rodden told the inquiry that she last saw Declan alive around the time of his first birthday, in April 2009, and that she had not been babysitting him when Kimberley said she had.
The inquiry also heard that Hainey told people Declan had been at a playgroup run by the social work department which didn't even exist.
Yesterday Mr Targowski, who is representing Hainey, said: "I do dispute there was extensive neglect.
"I find it very difficult to see what is meant by extensive, whether it was every day that Declan was neglected or the odd day over several months."
Hainey, 39, was jailed for a minimum of 15 years in 2012 after being convicted of neglecting and murdering Declan.
But she was released last April on appeal after a three-judge panel quashed her conviction.