Two women and a man have been arrested in the North in connection with the murder of schoolboy Thomas Devlin.
The 15-year-old was attacked in north Belfast in August 2005.
He was stabbed up to five times in the back as he walked home along Somerton Road after buying sweets from a garage.
PSNI officers believe the killers may have come from the loyalist housing estate Mount Vernon, where one of the women was arrested.
It brings to 15 the number of people detained for questioning in relation to the murder - no one has yet been charged.