"It is clear we have come to a point that we will not reach a unanimous agreement on any of the four charges," read a note from the jurors. The jury was then placed under a gag-order by the judge.
Porter is one of six officers charged in the death of Freddie Gray last April.
The 25-year-old Gray was arrested by Baltimore police and placed in the back of a van for transport. While his feet and hands were shackled, authorities broke protocol by not attaching Gray’s seatbelt, a decision which prosecutors say led to a high-impact spinal injury causing his death.
"Officer Porter knew how serious the injury was," Bledsoe argued.
Freddie Gray’s death led to widespread rioting in Baltimore. Police are preparing for additional violence in the wake of the Porter verdict.
Following the declaration of a mistrial in Porter’s case, two activists were arrested.
Porter is expected to be a key witness in subsequent officer trials, including that of Officer Caesar Goodson. The late date of his retrial could affect those plans, however.
Goodson faces the most serious charge of any of the six officers, second-degree depraved murder, and his trial is set to begin Jan. 6.