The Sunday Times reported yesterday that he is set to pocket just €16k from his late father’s fortune.
But estranged relatives claim he handed himself back to the authorities so he can legally claim his mother’s money.
“We read the article and laughed,” said one article.
The paper quoted “sources close to Gallagher” as saying that he returned to the Central Mental Institution in Dublin so that he could “put his past behind him.”
But a relative said: “He knows that if he is still legally insane when his mother dies, he won’t be able to get a cent.”
She inherited €300k when her husband died three years ago. Margaret Gallagher is also said to have her own fortune.
Gallagher absconded in 2000, 12 years after shooting teenager Anne Gillespie and her mother Annie, from the Twin Towns, in the grounds of Sligo General Hospital.
The killer is trying to be declared sane – and is expected to be freed to return to his native Lifford in July.