Evidence Recovery: What You Need to Know Solve the Crime

By: Michael S. Glenn

Emergency response divers play a vital and critical role in the investigative process. This is especially true as it relates to an incident involving local waterways. For all intents and purposes, every dive operation has the potential to be an evidentiary dive. Emergency Response Diving International has taken several advanced steps to ensure its dive team family is well versed in this arena of diving. This helps to ensure professionalism and proficiency in underwater criminal investigations.

The effective recovery of items of forensic interest, more commonly called evidence, is paramount to the success of any legal proceeding. These items:

  • Aid in illustrating the testimony of the witnesses.
  • Re-create the mechanical aspects of the incident.
  • Establish a pattern of what actually occurred (Actus Reus).

More importantly, the evidence can aid investigators in establishing who was involved. As such, proper recognition, location, collection, and handling of these items are of the utmost importance to the emergency response diver. Emergency response divers should become trained and well versed in understanding what additional items may be obtained from the fruits of the dive operation and recovery attempts. Knowledge of forensic capabilities will aid in mission preparation and planning the recovery mode.


In the underwater arena of criminal investigations, the emergency response diver is the crucial component to the investigative process. As such, they should understand the fundamental aspects of their operations as it relates to possible litigation and evidentiary admissibility. Also, the underwater environment changes from moment to moment and day to day. Factors including flooding, rainfall, pollution, and even basic water movement can all impact the underwater scene and the integrity of the evidence sought.

As such, it is important that dive teams are able to respond as swiftly as possible. Doing so will help them accurately locate items before environmental damage may occur. Factors including: manpower, safety, weather and even traffic may impact response times. Teams need to plan for their overall safety while trying to secure the scene efficiently. The more readily and rapidly the evidence is located and properly recovered the more likely its forensic validity may be maintained.


All criminal investigations and crime scene investigations work on the premise of Locard’s Theory: (Oversimplified), “. This can be summarized as, “An exchange takes place between the person and the object or environment when they come into contact with one another.”

For example, when a person stands on the shore and throws an object into the water, the person’s fingerprints, sweat, skin and even minute fragments of fabric, from their clothing may be found on the item. Additionally, the soil, water, and microscopic materials in the environment may attach the subject’s shoes, pant legs, clothing, and skin. As such, every item has the potential to contain smaller minute items of forensic interest. This can include items such as:

  • Fingerprints
  • Trace evidence
  • Tool marks

Forensic research has shown that additional items, previously unheard of, can be gathered from some of these items; for example: fingerprints. Fingerprints have been further examined to find DNA from the sweat and oils left in them. Also, trace evidence including clothing fibers, narcotic residues, and explosive residues have also been found trapped in fingerprint oil secretions.

These advancements in forensic capabilities have made suspect identification more accurate. They have also aided dramatically in reducing false suspect creation which has previously led to erroneous detentions.


Evidence generally falls into three basic categories: physical, illustrative and circumstantial.

  • Physical items of evidence are the actual items used in the planning, execution and obtained by the commission of a criminal act.
  • Illustrative evidence may fall into witness testimony, responder’s recollection of their actions at the scene or photographs introduced to show the scene as it appeared during the response phase.
  • Circumstantial evidence is the vaguely implied components that are often introduced without anything to directly connect it to the specific incident. Examples of circumstantial evidence would include that the individual was behind on the vehicle payments and then the same vehicle is found disposed of and submerged.

For the context of this article, we will be limiting our focus to physical evidence.

Due to the fragile nature,  and ease in which evidence can be altered, damaged and even destroyed. Divers need to take all precautions to avoid potentially damaging any item they may encounter. Also, every available attempt should be used to avoid cross-contamination of the item of evidence with the individuals’ selected diving mode or teams’ recovery practices.

One standard rule in underwater evidence recovery is all evidence must be recovered while continuing to be in the water it came from. Exposure to air may cause oxidation or rust. This could eliminate any potential for further forensic development techniques to be used. Further, just as land-based crime scene investigators encapsulate themselves to avoid contaminating the scene, divers should also do the same with the use of appropriate dry suits and gloves.


Divers should not handle or collect items of evidence with their bare hands. It is potential, albeit rare, that the diver could transfer their own fingerprints to the object or place their fingerprints directly over the suspect’s. Failing to wear gloves could make forensic comparison much more challenging, if not impossible.

Additionally, during searches divers need to be careful to avoid silting out the area to the best of their ability and the scene allows. Silt acts as a mild abrasive, similar to fine grit sandpaper. Fingerprints , via chemical analysis, are roughly 99%-99.5% water. The remaining 0.5%-1.0% containing oils, fats and amino acids, etc. Mild abrasiveness could wipe the print from the surface of the object. The same abrasive nature could also damage trace evidence which had been attached to the item of evidence in question.

In contradiction, most forensic examiners have been led to assume that fingerprints could not be obtained from surface previously submerged in water for extended periods of time. This belief was that the water itself would obliterate and destroy the fingerprints water base. However, repeated experiments and practices have shown that the use of a liquid fingerprint powder, Small Particle Reagent (SPR), can in fact recover fingerprints from objects having been submerged for several days and weeks.

Trace Evidence

Trace evidence located on recovered items can show the environment where the item originated. This can help investigators understand its association to the crime. Fingerprints can show who was in contact with the item(s) and be compared back to a specific person. Specific trace components found can further illustrate and confirm suspect identity. They can even provide additional illustrative components to the suspects

Treating the underwater crime scenes in the same manner that land based crime scene investigators will greatly improve the professionalism and proficiency of the diver in searching, locating and recovering evidence. The evidence recovered, if handled properly, can further enhance its usefulness to forensic practitioners.

  • It can help in identifying individuals associated with the specific item.
  • Its recovery location can also help in understanding the mechanics of the actual incident of disposal or submerging.

Divers are highly encouraged to seek a working relationship with local law enforcement investigators and technicians. They should also seek training in criminal investigation techniques. This will assist in ensuring compliance with recognized industry standards on evidence handling. Further information may also be obtained in the Emergency Response Diving Operations courses through International Training.

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