Joyce Plotnikoff, adviser to the Judicial College of England and Wales, said Scotland is missing the opportunity to protect the most vulnerable witnesses because it refuses to introduce intermediaries - trained staff who help children and others to convey evidence in court.
She spoke out after a convicted killer and sex offender was acquitted last week by appeal court judges. Mohammed Akram, 53, was freed after appealing against his life sentence for indecently assaulting a four-year-old girl.
Akram had protested his innocence since the allegation against him was first made. Giving evidence at his trial via CCTV, the girl, then aged five, said a man had "touched her".
Appeal court judge Lord Eassie, sitting with Lords Bracadale and Wheatley, watched footage of the child's marathon court ordeal. They said her attention wandered, she tried to leave the room and refused to answer questions.
Lord Eassie said: "By the second day, if not earlier, the child had been rendered incapable of engaging meaningfully with the process of giving evidence."
The judge said because of that, the girl could not be questioned properly by Akram's lawyer.
They also agreed the way trial judge Lord Brodie gave the jury instructions on how to consider DNA evidence and whether it backed up the little girl's story constituted a misdirection.
Advocate depute Iain McSporran, for the Crown, conceded it was "a material misdirection" which amounted to a miscarriage of justice.
After he was initially convicted of indecently assaulting the girl on New Year's Day in 2011, it was revealed Akram had served five years in 1979 for culpable homicide.
In 2003, he was jailed for eight years for a sex attack on a 16-year-old student and he was still on licence at the time of the 2011 allegation. Lord Brodie judged Akram to be a danger to the public and placed him on a lifelong restriction order.
Ms Plotnikoff is co-director the Lexicon Centre and has also worked as an attorney adviser and probation officer in the US.
"This would almost certainly not have happened in an English court," she said.
"Next year is the 10th anniversary of the introduction of intermediaries - communication specialists who assess vulnerable witnesses and advise the judge and advocates [on] how they should be questioned.
"Scotland has held two consultations on their introduction, but has done nothing about it. Another opportunity is about to be missed, as there is a Victims and Witnesses Bill before the Scottish Parliament with no provision for this special measure.
"We evaluated the intermediary scheme here when it was introduced - it has permitted evidence to be taken successfully from four- and five-year-olds, as well as older children and vulnerable adults. More than 6000 intermediary appointments have been made."
Organisations including Children 1st have campaigned for intermediaries to be introduced.
A Scottish Government spokeswoman said: "Our Victims and Witnesses Bill was developed in close dialogue with and widely welcomed by victim support organisations and victims of crime in Scotland.
"It will create a duty on justice organisations to set clear standards of service, give victims and witnesses new rights to case information, allow them to address the parole board about the release of life-sentence prisoners and establish a victim surcharge so offenders contribute to the cost of supporting and assisting those affected by crime.
"We are already committed to holding further dialogue on whether to pilot additional special measures, including seeking views on the possible role of intermediaries."