A judge-led inquiry into undercover policing methods is to open.
Appeal Court judge Lord Justice Pitchford will deliver his opening remarks in the first hearing of the public inquiry, ordered by the Home Secretary to look into police infiltration of political and social justice groups in England and Wales since 1968.
Theresa May announced the probe in March after controversy over the revelation that Scotland Yard spied on campaigners fighting for justice for murdered teenager Stephen Lawrence.
An independent review led by Mark Ellison found in March last year that an officer in the Metropolitan Police's now-defunct Special Demonstration Squad (SDS) had provided information on the Lawrence family.
The separate police-led Operation Herne found that the SDS unit carried out undercover operations to collect information on 18 justice campaigns over the course of 35 years.
Stephen's mother, Doreen Lawrence, has called for the inquiry to name covert officers, whose identities are usually kept secret.
Lord Justice Pitchford will be able to access documents and call witnesses to give oral and written evidence to draw up a report for publication within three years, which will include recommendations on the future use of covert policing.
Mrs May has tasked the inquiry with assessing the adequacy of "justification, authorisation, operational governance and oversight of undercover policing; selection, training, management and care of undercover police officers; and ... the statutory, policy and judicial regulation of undercover policing".
And the investigation will include a review of forces' duty to disclose the existence of undercover operations during criminal trials and an assessment of the scope for miscarriage of justice where they are not disclosed.
Any possible miscarriages of justice uncovered by the inquiry will be referred to a panel of senior members of the Crown Prosecution Service and the police, which could refer the case to the Criminal Cases Review Commission.
The inquiry will look into the use of covert human intelligence sources by all English and Welsh police forces, including the targeting of political and social justice campaigners and the activities of the Special Demonstration Squad and the National Public Order Intelligence Unit.
Reporting to the Home Secretary, it will make recommendations on the future deployment of undercover police officers.