The below statement can be attributed to Karen Sheley, Police Practices Project Director, ACLU of Illinois:

"It is incredulous that the Chicago Police Department has chosen this moment – a time when people are re-thinking our fundamental notions about policing and how we police our City – to reduce transparency into the activities of officers by taking down critical arrest data. Policing in Chicago can no longer be an insular, unaccountable force. This behavior only drives a further wedge between CPD and Black and Brown communities across the City. 
Holding the Department and individual officers accountable for their actions on the streets of Chicago requires comprehensive data is available to journalists, academics and the public. Arrest data is fundamental to any meaningful analysis and public input. That the City has pulled down this data because of criticism and questions raised in the media is both silly and shameful. This data must be restored to public view."