Council chiefs told police have "reasonable grounds" to suspect the offence may have been committed.
His mother says: "We've had no control over our son's life and no control over our son's death."
Macey Hogan was killed after her mum sent the toddler's father "one last picture" of her.
The Cartier ring was reported missing in August 2011 but its loss has only just been revealed.
A government adviser on equal pay says women are "less proactive" in asking for more money.