But laying a new charge wouldn't have any effect on Smith's punishment. He is serving a life sentence for murder and child sex offences.
"The only real effect of charging him would be there's a public trial and then he gets five years' imprisonment, which effectively just means he can't apply for parole for the next five years, but there's not a parole board in the country that would let him out anyway.
"It's a waste of time."
Dr Ellis said he believed Smith could realistically be spending life behind bars, and a trial for escaping custody wouldn't change that.
"On a straightforward, rational basis, I don't think it is in the public interest."
Smith and his police escorts boarded a flight from Rio de Janiero to Chile. He was expected to catch a flight from Chile to Auckland that would land about 4am today.
Smith fled on November 6 using a passport issued in his birth name Traynor. He was captured in Rio at a backpackers hostel on November 13.
NZME.