Drones for Law Enforcement and Evidence Collection
Written by Greg Bishop   

This article appears in the July-August 2021 issue of Evidence Technology Magazine.
You can view that full issue here.

THOSE IN THE FIELD OF LAW ENFORCEMENT are realizing the advantages that drones and unmanned aerial vehicles (UAVs) can offer in documenting events in real-time, as well as providing useful tools for gathering evidence. Most are familiar with dramatic road chases captured by UAV or helicopter, as well as cases of lost and stranded hikers and campers located by drone-assisted search-and-rescue teams. But these occurrences are relatively rare compared with the advantages of an eye in the sky in non-emergency situations; scenarios that require quick decisions; and, increasingly, in evidence collection and documentation. Some law enforcement organizations realized this early in the days of drone technology. And as prices come down and advanced options increase, more jurisdictions are getting on board with these advantages.

Documentation of traffic accidents, investigations of fires or other destructive events, and mapping of crime scenes from places too high or dangerous for a ladder (and too low for helicopters) are finally achievable with the use of off-the-shelf consumer and prosumer drones. Sergeant Caleb Curtner, an unmanned aerial systems officer for the Riverside County (California) Sheriff’s Department, said the organization’s first use of drone technology was in 2016 to assist in search-and-rescue operations. But, he said, “as the program progressed, UAVs and small unmanned aerial systems (sUAS) were deployed in other department functions and criminal investigations, such as aerial imagery, media production, missing person investigations, community events, and other assignments as directed.” Riverside County has even used the drone fleet for locating homeless camps, as part of the department’s Homeless Outreach Team.

Other departments have reported similar trajectories in setting up their own programs, realizing the utility of sUAS and expanding use in a multitude of scenarios and applications.

Sergeant Robert Dewey, body camera and sUAS Unit supervisor for the Fresno (California) Police Department, recalled that his first “test pilot” was an officer—also a licensed commercial pilot and FAA certificate holder—who used his own consumer UAV for about a year to determine the usefulness of the procedures. Once it was decided that the technology was viable, the department began acquiring what has grown to become a fleet of 40 prosumer drones flown by 18 officers. The fleet has operated for a little over a year as of this summer.

Officers with the Fresno Police keep UAVs in their cars and deploy them as needed. Dewey said that personnel are not actually assigned to pilot responsibilities full time. Instead, it is an extension to their normal job descriptions, and new officers are continually being added as others are transferred to different duties and divisions.

To fly as a part of work for hire or as a paid employee, all UAV pilots must have approval from the Federal Aviation Administration, either in the form of “Part 107” remote pilot’s license or a blanket “Certificate of Operation” (COA) from the FAA. Dewey’s officers operate under this certificate, while other departments (such as the San Diego County Sheriff’s Department) require all officers operating drones to complete a formal in-person course and supplemental training in department policy and procedures, as well as regularly scheduled refresher classes to remain abreast of changing situations and regulations.

Drones have proven useful in gathering information and evidence either from a high vantage point, or even from ground level.

Drones have proven useful in gathering information and evidence either from a high vantage point, or even from ground level, keeping officers out of harm’s way until a situation can be resolved—as well as in cases like suicide prevention or other tense standoff scenarios. Dewey recalled a particular case involving a suspect in a convenience store who was subdued without incident when an officer flew a DJI Mavic 2 Enterprise UAV into the store equipped with a 100-decibel loudspeaker which was used to convince the suspect to surrender. “We never had to put any officers into the situation,” he said.

The drone can either broadcast live audio or store up to ten 60-second voice recordings that can be uploaded to the unit and played back on demand, another example of the platform’s design and usefulness for public safety personnel.

Sergeant Robert Samuels III of the San Diego County Sheriff’s Department echoed the safety angle, and added that “during high-risk situations, the use of the UAV has the potential to save lives not only of our deputies but members of the public, regardless of their involvement in crime.”

He added, “Being able to use a UAV to create a safe stand-off distance and provide real-time information helps to prevent those ‘surprise’ encounters where split-second decisions need to be made with no information. Now, we often have the ability to observe a situation and develop a plan to help resolve things safely.” Samuels also remarked that his department has “nearly 60 UAV pilots working all over the county.”

The Mavic 2 Enterprise Dual, released in December of 2020, was marketed as an affordable platform for law enforcement and search-and-rescue applications, and has proven to be useful as advertised. It features a 2x optical zoom and a 3x digital zoom on the visible light lens and imaging system, in addition to a FLIR system which operates in the infrared spectrum—offering a view of the scene which is valuable in finding suspects hiding in the dark, as well as heat signatures of objects and evidence that would be missed in a normal investigation.

According to Dewey, the Enterprise Dual is best suited for “indoor searches and traffic stops,” although he usually encourages his officers to use the DJI Mavic Mini, since it “does a really good job for about 80% of the missions”. The Mavic Mini gets flown more often since its replacement price is about $400, as opposed to the Dual at $3,000—and the Fresno Police Department has far fewer of the Enterprise Dual models available.

In evidence documentation and collection, UAVs have proven to be a most valuable tool and adjunct to traditional methods such as surveys, mapping, and on-the-ground photography. “It’s easier to put things in perspective when you are able to see things from above,” said Samuels.

A surprising benefit of UAVs is their ability to recreate the scenario of a fleeing suspect, giving prosecutors and legal teams another tool to determine where the person was going, what obstacles and hazards were encountered, and possible decisions involved in efforts to evade capture.

Two of the organizations contacted for this article noted that a surprising benefit of UAVs is their ability to recreate the scenario of a fleeing suspect, giving prosecutors and legal teams another tool to determine where the person was going, what obstacles and hazards were encountered, and possible decisions involved in efforts to evade capture. Samuels, with the San Diego County Sheriff’s Department, noted that “video is useful when you want to take the viewer on a journey, so to speak, such as flying the path a criminal took during the commission of their crime.”

Dewey said the Fresno Police can “fly the drone along the path, between buildings, over a rooftop, etc.” then, during legal proceedings, “the jury and DA can see this and get context.”

Another benefit reported by Dewey is the use of drones in recreating the point of view of a witness. The aircraft can be stationed at the reported or remembered location and provide a first-person view of the scene, as well as an overall look from any vantage point to confirm or refute recalled memories and testimony, providing further evidence in pursuit of a just prosecution.

Drone images and footage have only recently begun to face the tests of courtroom prosecutions. According to Curtner, the Riverside County program has so far only given the images and video to case agents for further analysis and integration with other forms of evidence collection. Samuels also relates that presently, the San Diego County Sheriff’s Department uses their drone footage and images “as a resource, so we don’t always get that feedback from investigators. We simply capture what it is they wish for us to capture with the UAV then turn it over to them.”

Surprisingly, most law enforcement contacted for this article said that their policy is to record video in 1080p resolution rather than at 4K, in the interest of keeping file sizes smaller. Samuels said that the San Diego County Sheriff’s Departments uses 1080p, as it is “a good compromise between resolution and storage.”

As documentation of crime scenes by UAV continues, and storage media become faster, smaller, and more affordable, this will certainly change. Still photos using prosumer drones is typically at 5400 x 3600 pixels, which is more than adequate for most applications. The quality of the images and video also depend on situational lighting and exposures, which can vary in quality. Dewey said the Fresno Police Department advises officer-pilots to keep the camera’s exposure settings on automatic unless they have some other photographic experience.

At first, recalled Dewey, their drones were simply asked to “do random flyovers” at the convenience of the situation and the officers who had the equipment to do the job. The use of sUAS units in the department is now nearly standard.

One of the first obvious uses of drones in on-the-scene documentation began with traffic stops and other vehicle incidents such as crashes, keeping officers out of harm’s way in dangerous situations where they could be injured or killed while concentrating on sketching or photographing the scene. As the advantages became more apparent, use has expanded. At first, recalled Dewey, their drones were simply asked to “do random flyovers” at the convenience of the situation and the officers who had the equipment to do the job. The use of sUAS units in the department is now nearly standard.

Another important emerging application of UAVs is for the documentation of crime scenes such as a homicide, which often occur at night. Dewey said that the Fresno Police will often return to a scene at different times of the day. This allows the department to record multiple images or angles as needed, to bolster or refute witness testimony or gain a perspective that was missed in previous scans or with ground-based methods, as well as to offer better resolution to reveal details that would be missed in the dark. While Samuels remarked that “we use imagery from our UAVs in all outdoor homicide cases,” Dewey said they have used drones in cases that have occurred indoors as well.

Another obvious advantage of an aerial view is finding evidence that may elude ground-based investigators—for example, “an object such as a weapon that may have been discarded up on a roof,” said Samuels.

In 2019, an evidence-specific drone dubbed “AirCSI” was in development for the Brazilian Federal Police. This drone recorded stereo imaging data along with GPS location data, as well as images of the scene that were recorded as a photomosaic (a series of images that are stitched together to create an overall map). The unit was programmed to autonomously zero in on areas of interest and concentrate on gathering images from multiple angles. This system is still being developed, but off-the-shelf units can already be utilized for the same or similar purposes, using multiple drones and mapping software such as DroneDeploy, which can create a 3D or elevation map or even a vegetation survey of a specific location.

Samuels said his traffic division “has been testing Pix4D software for vehicle accidents,” and has “conducted flights to be used in renderings of locations such as the San Diego Fairgrounds.” This may be required, for instance, in preparation for an area experiencing large crowds, possibly for weeks at a time, so that the information would be available for quick reference later.

Since they were introduced into law enforcement, UAVs have become invaluable tools. One of the main issues that now faces various jurisdictions is convincing lawmakers and officials who hold the purse strings to budget for them. Curtner recalled that, at first, “the main advantage in collecting aerial still and video imagery with a UAV/UAS [was] cost effectiveness vs. using the helicopter.” As with any electronic technology, as the products improve, the cost often drops significantly—and the public is starting to see and accept their use in criminal investigations, even as surveillance and privacy issues around drone use continue to be fought in the courts.

Perhaps the best summary of the advantages of UAVs in law enforcement was provided by Samuels. “It is still a relatively new resource for many, and it requires some out-of-the-box thinking from traditional photography and investigative measures,” he said. “As we use the UAVs in investigations and as prosecutors see the usefulness of the UAV video and photography, their use expands.”

About the Author

Greg Bishop is a lead instructor for Drone Universities, LLC specializing in FAA part 107 test preparation, safety, mapping technology, and operations.

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