In March 2010, as Fox31 reported, Diaz and another officer, Jeff Cook, made a traffic stop near Mark Ashford, 32, who was taking his dogs for a walk.
Ashford offered to testify on behalf of the driver pulled over by the two cops, who responded by detaining him and asking to see some identification. Along the way, Ashford tried to take a photo of the officers. He didn't succeed, but another camera captured what happened next. Diaz and Cook punched Ashford and took him to the ground, after which he was arrested on suspicion of resisting arrest.
That charge was later dropped, and Ashford, who had to be checked out at a hospital after the pummeling, hired an attorney to file a complaint alleging excessive force on the part of the officers. Before a final determination was made, however, Diaz resigned, in August 2010.
The resolution of the matter sent something of a mixed message.
In March, news broke that the Office of the Independent Monitor, tasked with reviewing such matters, determined that Cook -- the only officer mentioned in the report, due to Diaz's resignation -- had not stepped over the line. The document states: "The officer had legal authority to stop the motorist and issue a summons... Officer Cook was also within his rights to contact (Ashford) and request that (Ashford) step back on the sidewalk and allow the motorist to continue on his way." In addition, the Independent Monitor concluded, "Video evidence captured by HALO cameras does not support (Ashford's) allegations that officer Cook used excessive force during the arrest."
In June, however, the City of Denver agreed to pay Ashford $35,000 in relation to the incident.
With that, Diaz faded from public view. But now, focus is on him again in relation to an incident this past weekend. Jefferson County Sheriff's Office spokeswoman Jacki Kelley told the Denver Post Diaz is accused of bullying his way into the South Jeffco home of his former wife and going after her current beau. The result: an arrest on suspicion of assault, domestic violence, criminal mischief and first-degree burglary.
This time, the Independent Monitor won't be weighing in -- meaning Diaz's fate could well be in the hands of a jury. Look below to see a Fox31 report from March, showing clips from the Ashford footage.
More from our Follow That Story archive: "Michael DeHerrera talks about reinstatement of cops who beat him (VIDEO)."