The difference between being detained or arrested in Scotland
Police have detained Alexander Pacteau, 21, in connection with the disappearance of student Karen Buckley
Under Scottish law, when police believe that someone has committed a crime, they can detain that person in custody for up to twelve hours.
This may, in certain circumstances, be extended by a further twelve hours.
At the end of the respective period the police must release the suspect unless they believe they have sufficient evidence to arrest them.
http://www.mirror.co.uk/news/uk-news/karen-buckley-missing-live-updates-5521618