Scipio I do think the Defence have a gripe when black canvas shoes are removed from a crime scene and a Police Officer tells Ann Eaton "you haven't seen those".
First of all she screwed it up. They told her she didn't see them take the paint samples. They didn't care about the shoes they spoke to her about clothes and shoes to try to support their lie they were there for the inquest because they didn't want anyone to know they actually went there to take the paint samples. She watched them take the samples and didn't want it to get back to Jeremy so told her she didn't see it which means keep quiet.
Second, They didn't want Jeremy to find out they didn't trust him because then he would stop cooperating. Cooperation not only meant enabling them to search the premises without needing a warrant, it means he would talk to them and potentially while talking they could get something useful out of him. If he knew they were suspicious then he would be even more apt to lie about seemingly mundane things. They would see mundane if he wasn't suspicious but he might see their reason for asking if he knew they were suspicious.
There is nothing improper about wanting to conceal the investigation from him.
Along with Doctor Hugh Cameron Ferguson's evidence which Carol Ann Lee now tells us the Doctor says Sheila was capable of murdering her children they are relevant issues for anyone seeking a retrial.
Ferguson's changed opinions many years after the trial are wholly meaningless. They were based upon things that never happened. Even if he simply changed his mind because he simply viewed the same set of facts differently it makes no difference it is not new evidence. His opinion is meaningless anyway because the evidence that convicted Jeremy was evidence that Sheila could not have killed herself and evidence that Jeremy told Julie he planned to kill them and admitted he was responsible. To refute guilt the prosecution has to undermine one of these two premises. Ferguson's opinions don't relate to either.