The junior Mr. Flake and his wife, Logan, 21, were caring for the dogs while Logan’s mother and stepfather — MaLeisa Hughes, 45, and Jesse Todd Hughes, 32, the owners of Green Acre Dog Boarding — traveled to Florida in June. During that trip, 22 of the 28 dogs that were held in the 9-by-12 room died, some with no food in their stomachs; the defendants say that one of the dogs chewed through a cord to the air-conditioner in that room, where most of the dogs were locked up for the night.

Public vigils for the dogs drew hundreds of mourners. Plans have been drawn up for a memorial at a park as a tribute to the dogs referred to as the Gilbert 23, including one who ran away from Green Acre and was hit by a car.

“It really shook up the community,” said Cary Heath, whose family lost three dogs: Happy, Cloe and Rosie. “The community has been behind us on this. I thought we were just completely betrayed and nothing would come of this, but we’ve met a lot of wonderful people and changed a lot of lives.”

Details of the case, including the voluminous report from Sheriff Arpaio’s office, have dominated the local news. One local resident called it the “dog equivalent of the Jodi Arias trial” — a news media circus of a murder case here.

Image Austin Flake, son of United States Senator Jeff Flake of Arizona. Credit... Maricopa County Sheriff’s Office

In October, a grand jury indicted the two couples on multiple felony charges related to animal cruelty, and the Hugheses also face fraud charges. The Hugheses pleaded not guilty last month. On Thursday, the Flakes are scheduled to be arraigned and will also plead not guilty, their lawyer said.

“These are two innocent people who have been going through a nightmare that’s really unfair when all the facts have not come out,” said Dennis I. Wilenchik, the Flakes’ lawyer. He also condemned the sheriff’s department’s investigation as “heavy on publicity but devoid of any evidence of criminal wrongdoing.”