The inquest looking into the death of Ashley Smith is hearing today from the first witness not called by coroner's lawyers.

Andrew Coyle is emeritus professor of prison studies at King's College at the University of London and has worked in the prison system throughout the U.K. He's been called to the stand by the Canadian Civil Liberties Association.

Coyle outlined how the prison system works in the United Kingdom and Wales, where an independent monitoring board is used to keep an eye on prisons.

"People who are laypersons, who are not concerned with the management aspects, are able to express a common sense view because, very often, the prison system, like any organization, will develop a whole mystique around its protocols and its procedures."

Coyle also says there are reasonable time frames for keeping someone in solitary confinement. The UN recommends 15 days.

Smith, the Moncton teen who died in prison in 2007 after tying a ligature around her neck, was kept in segregation for much of the 11½ months she was in federal custody.