In an interview with Children in Scotland's magazine, the former director of the Scottish Child Law Centre says that she intends to be outspoken on the issue.
"We often start out talking about child protection and end up talking about adult protection, ie how adults can protect themselves from being blamed when things go wrong," Mrs Marshall states.
She lost no time in making it clear she would be no slavish follower of the Scottish Executive or the Scottish Parliament which appointed her. On the day she was due to be confirmed in the post, she spoke out against the detention of children from asylum-seeking families and later declared she was unhappy with the compromise reached on smacking children.
In her interview, Mrs Marshall declared that smacking "is not an issue that is going to go away". She pointed out that she had long been part of the "Children are Unbeatable" movement to give children the same rights to protection as adults, and suggested a campaign to win over parents.
The new commissioner also signalled her disenchantment with the Antisocial Behaviour Bill, in particular tagging children.
Mrs Marshall continued her confrontational reputation this week at a conference to launch a book, Honouring Children, co-authored with Paul Parvis, an honorary fellow at New College, Edinburgh University. It examines whether Christianity is opposed to children's rights.
Let them be heard, Friday magazine