About Us


The history of this agency began over fifty years ago with the work of Sal Dena, a former US Marine turned narcotics and homicide investigator, who founded SAL DENA PRIVATE DETECTIVE INC in Seattle in 1974. During his distinguished career, Sal was at the forefront of the private investigation industry, and investigated all types of cases both nationwide and abroad. He was also regarded as one of the leading authorities on ritual homicide, ritual abuse, and occult-related crime, and was often consulted by law enforcement agencies for his expertise in those fields. He assisted them on the cases of Ted Bundy, Gary Addison Taylor, Jeffrey Dahmer, the Son of Sam, the Atlanta Child Murders, and many others. Being a devout Christian, Sal was able to investigate these heinous crimes with a Biblical perspective, which gave clarity to his investigations and made his help greatly sought.


When Sal retired, he authored two books recounting some of his cases and gave frequent lectures on the subject of ritual crime. Although he was retired, the cases continued to pour in, brought to him by clients who had been the victims of these crimes or law enforcement agencies that had not been trained to investigate them. Recognizing the lack of formal training in this field, Sal began educating and preparing other like-minded men and women to carry on his work. Sal worked with these associates to help the clients who were still reaching out to him, and also looked into many cold cases that had been given up on by law enforcement. In addition to investigating cases of ritual crime, they also worked on many standard cases such as missing persons and homicides. They investigated these cases pro bono, with their only motivation being to help others find answers and healing.

One of the associates who worked closely with Sal was Sheridan Gleason. Sheridan began his career as a private investigator interning with a large agency in the Los Angeles area, where he gained extensive field experience in all aspects of investigative work. In 2008, he started working as a security consultant in the Seattle area, in the fields of counterterrorism, organized crime investigation, loss prevention, executive protection, and physical security. Also a devout Christian, Sheridan first met Sal at church, where they immediately became friends. They started working together in 2011, and for over a decade Sheridan assisted Sal with many cases in various parts of the country, investigating ritual crimes, cult activity, homicides, missing persons, and cold cases.


In 2023, recognizing the need for a full-service private investigation agency to carry on their work full time, Sheridan founded DENA & ASSOCIATES INVESTIGATIONS LLC for that purpose. He named this agency after Sal Dena to not only honor him as a mentor, but also to recognize his contributions to the private investigation industry. We are committed to carrying on the tradition of investigative excellence that defined Sal's career for over fifty years. We investigate all types of cases for private individuals, businesses, insurance companies, and law firms. Some of the cases in which we specialize include homicides, missing persons and cold cases, and we are also one of the only private investigation agencies in the world that is equipped to investigate ritual crimes and cult activity. For more information, visit our Services page or contact us directly for a consultation.

Dena & Associates Investigations LLC
Washington State Private Investigator Agency License Number: DOR00030886

Sheridan Gleason, Agency Principal
Washington State Private Investigator License Number: 23031603

Phone: 206-919-2538
Email: info@denainvestigations.com