Earlier this year it emerged those accused of a crime can self-declare their gender without providing any evidence.
But Police Scotland has been unable to confirm when that change was made, saying the policy “evolved” over time.
Academics have argued the introduction of gender self-identification has significant implications for the accuracy and reliability of crime statistics, amid claims a small number of transgender suspects could “skew” the data.
Police Scotland was asked under Freedom of Information legislation when it stopped recording incidents according to a person’s biological sex and began recording according to self-identified gender.
A force spokeswoman responded: “I can confirm that there was no ‘effective date’ for this process, rather it has evolved as best practice and ensures all people are treated fairly and with respect, in line with the Police Scotland Code of Ethics.
“With regards to victims, witnesses and suspects, Police Scotland have always treated people as they present, and incidents are therefore recorded according to a person’s self-identified gender/sex.
“We require no evidence or certification as proof of gender identity other than a person’s self-declaration, unless it is pertinent to any criminal investigation with which they are linked and it is evidentially critical that we legally require this proof.”
In March, justice secretary Humza Yousaf told MSPs that this was the case.
Kath Murray, a criminologist who is part of policy analysis group Murray Blackburn Mackenzie, said: “The unregulated introduction of gender self-identification principles in the Scottish criminal justice system has significant implications for the accuracy of recorded crime data.
“We are also concerned about media reporting on offending behaviours that have a clear sex-based pattern in the population.
“Males are disproportionately responsible for violent and sexual crime, and being able to name the issue of male violence is vital, both at an individual and a societal level.”