(CNN) The release of cell phone video taken by Sandra Bland almost four years after her death and nearly two years after the trial for the trooper who arrested Bland makes her sister question what the police have told their family.

Bland's sister Sharon Cooper said the lack of transparency from investigators throughout this process has been an issue.

Sandra Bland

"The revelation of this video existing to us and it not being revealed to us throughout the duration of the case at all, what that does is that puts our trust in them and their credibility on shaky ground with regard to taking what they share with us at face value," Cooper said.

Cooper said the family decided to filed a civil rights lawsuit following Bland's death because they "weren't getting answers to the questions" even after multiple inquiries on her sister's case.

"Our faith in the Texas Department of Public Safety along with (Waller) County officials has never been on solid ground because of their consistency with being nontransparent and not sharing information with us and instead sharing it with other parties."

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