Campaigners want Home Secretary David Blunkett to order a full inquiry into the trial of Sion Jenkins for the murder of his foster daughter.
The former deputy head was jailed for life for battering Billie Jo Jenkins to death at the family home in Hastings in 1997.
Now the Justice for Sion Jenkins group is urging Mr Blunkett to order an inquiry into Jenkins' conviction, which it said has caused them "deep unease".
The group said allegations of police brutality in Hastings town centre made in July by Michael Smith, 44, had reinforced their concern at Jenkins' conviction.
Jenkins was head teacher designate at William Parker School in Parkstone Road, Hastings.
Since the trial, campaigners have been fighting for his release, saying the evidence was flawed.
A spokesman for the group demanded: "How much more evidence is needed to show that something is very wrong?"
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