Murder of Alesha MacPhail
"I feel angry, upset and I'm losing the trust or the faith I had in the justice system," said MacPhail's uncle.
The six-year-old was raped and killed on the island in July last year.
The teenager was convicted of abducting, raping and murdering the six-year-old.
The 16-year-old faces a minimum of 27 years in prison.
The 16-year-old was jailed for life this week.