loot and scoot
Greenie
- Feb 24, 2010
- 15
- 2
This is an article I wrote several years back describing the use of a dredge by our dive team. It was published in Underwater Magazine and a couple of online forums. I would be interested in any feedback by forum members on how to improve this technique.
Law Enforcement use of Dredges in Evidence Recovery
By Deputy Sheriff Brian Hanger
Polk County Sheriff’s Office (Florida)
The evolution of public safety diving for a majority of agencies has seen incremental but steady progress in the areas of equipment, training, and evidentiary procedures. Over the last twenty years, many agencies have progressed from small volunteer teams to specialized units within the department. Often these early teams consisted of members from a variety of backgrounds and provided their own equipment. Training was infrequent and employment of the teams was limited to the recovery of objects that were discernable by touch. The classic “grope on a rope” is still a viable search technique but is often limited due to bottom conditions and size of the object. This article will examine the use of small dredges in the recovery of evidence by public safety dive teams as an additional method in evidence recovery.
As a member of the Polk County Sheriff’s Office (Florida) underwater search and recovery team (USART) for the past eleven years, I have witnessed my own team’s transformation from a basic volunteer organization to a capable specialized unit. My beginning experience as a new diver with USART was showing up for my first dive with my personal gear to a nearby lake and searching for a stolen vehicle in the water. After a series of rope sweeps I collided with a large immovable object that I determined to be the vehicle. A majority of Central Florida water bodies have zero or close to zero visibility forcing the diver to use their imagination when encountering an object. The general rule for divers was to return to the surface with any object they thought was the search item or mark anything too large to move with a buoy or rope. This works well for large objects like stolen vehicles. The difficulty starts when the search item(s) are small.
My next dive was an evidence dive for the homicide unit. A man was suspected of shooting his wife with a small caliber handgun. The suspect denied involvement in the crime and detectives where unable to locate the murder weapon. After a series of interviews with associates of the suspect, detectives learned of an incident in which the suspect and a friend were target shooting into a local canal. The friend of the suspect described the suspect using a handgun of the same caliber as the murder weapon and was willing to testify to the incident. Homicide detectives then called the dive team to search the canal for spent bullets for comparison to the bullets recovered from the victim’s body. A match would give the detectives a solid case.
Upon arrival the dive team set up a standard rope search and equipped the divers with underwater metal detectors. The search barely progressed a foot when the diver stopped to recover a signal from the metal detector. After several moments a fishing weight was recovered. The search began again and another foot of progress recovered pull tabs and fish hooks. The third foot searched revealed numerous 45 caliber bullets which where not the caliber we were searching for. An hour of searching had covered approximately ten square feet of lake bottom next to the shore and a growing pile of trash. Detectives watched the painfully slow progress and made a mental calculation that the potential search area of a bullet trajectory could be huge. A decision was made to search the immediate area next to the shore out to 60 feet. The dive continued to produce large amounts of trash and other incorrect size bullets. At about twenty feet from shore the divers encountered the beginnings of a deep silt layer that was over the reach of the diver’s arm. Metal probes were used to find the lime rock layer under six feet of silt. This prevented the metal detector signal from reaching any bullets that had penetrated the silt or hand excavation by the divers. With this information passed to the detectives it was determined that we could not discount or prove the suspect fired the murder weapon into the canal. This dead end started the search for a new method of small evidence recovery.
In my search for a new method of small evidence recovery I began searching the internet for equipment use to find small objects in the water. The most similar concept I found to evidence recovery was recreational gold dredging. Recreational gold dredging relies on the venturi principle; water passing through one side of a forked pipe will draw suction on the other side of the fork. With a hose attached to the suction side of the pipe a person could then draw the material through the hose and pipe and have the contents deposited in a basket. This method would accomplish my needs of moving material in such a way as not to damage evidence by passing items through a pump. The basket would be substantially different than a gold dredge so that a majority of the sand would fall through the screen and leave whatever size item the screen was designed to hold. Gold dredges must process this sand through a riffle system to find gold dust and small nuggets in the sand. My needs were for a system that would only hold the size item I was looking for and quickly pass the silt and sand back to the bottom. With a few modifications I believed I had the answer I was looking for.
I decided on a personal purchase of equipment from Keene engineering in California and built a somewhat makeshift dredge to begin experimenting on evidence recovery. The motor and three inch trash pump was placed in a small aluminum Jon boat connected to the water intake and venturi pipe. The silt and debris was pumped through the venturi pipe into a floating basket approximately four foot long and two foot wide next to the boat. The floats were made from eight inch PVC pipe capped at each end and tied with rope to the basket. This entire set-up would be put to the test soon after completion.
The dive team received a call for assistance from a local law enforcement agency to search for a handgun used in a shooting from a local lake. The lake is in the center of town and has over a hundred years of run off from the city streets drained into the lake. We set divers in a normal rope search pattern from the shore at the point the detectives believed the gun was thrown. The first several feet was covered in bottles and trash and was removed by hand. At approximately fifteen feet from shore, the silt was over the arm of the divers. Sixty feet from shore, the water was six feet deep and the silt was still over the reach of a diver’s arm. This would be the first real test of the dredge. The next day the dredge and boat was set up and a pattern was begun from shore. The first problem realized was that a three inch hose would not pass the average bottle or can. This lead to numerous stoppages in order to clear the vacuum hose of obstructions. We underestimated the sheer volume of bottle and cans that had accumulated in the downtown lake. Bottles and cans in the hundreds were encountered with silt over seventeen feet as we dredged into the lake. I came to the conclusion that a small three inch pump powered by a five horsepower motor was not up to the task for the volume of material that need to be searched. We now currently use a five inch dredge that can pass bottles and can to the basket and can be removed by the topside tender(s) and allow the diver to remove the maximum amount of material.
One concern that was raised by the city parks and lakes manager was the issue of water quality as the result of dredge usage. A previous meeting with the state Department of Environmental Protection and Southwest Florida Water Management District had been conducted to address water quality and permitting issues. Both the DEP and SWFMD agreed that we would be exempt from permitting based on the infrequent use, use by a law enforcement agency and we would inform them of times and places where the dredge would be operated. The city parks and lakes manager was also helpful in documenting the limited area of turbulence from the dredge. Our experience is that the dredge used in lakes and streams will create a turbulence area similar to that of a rainstorm runoff in an area approximately thirty feet in diameter. Generally material lifted from the bottom will return to the bottom in a short time.
Our agency experienced a tragic loss when a department helicopter crashed in a phosphate mine reclamaintion lake killing two of our members. The dive team responded and conducted the initial recovery of the pilot and co-pilot along with the main fuselage of the aircraft. After several days of diving to recover smaller fragments of the aircraft for the crash investigation, we received a request from the pilot’s wife to recover his wedding ring. The dredge was employed at the crash site and recovery of numerous fragments of the aircraft and personal effects began. The ring was recovered along with every bullet assigned to the officers as well as gauges and other items of evidence.
Investigation of aircraft crashes relieves heavily on the recovery of gauges due to the effect of “needle slap” on the gauge at the moment of impact. The investigator can determine the aircraft’s engine, flight, and mechanical status leading up to the crash. Every part of the aircraft recovered can be tested for metal fatigue, placement or pre-crash damage to give a more complete analysis of the accident. One missing piece of the aircraft can give rise to a legal question of doubt in the enviable civil litigation. The most complete recovery possible will be the standard dive teams are held accountable.
This recovery was done after a week of diving by our dive team and Orange County Sheriff’s Office dive team. Divers were faced with zero visibility water along with heavy vegetation and the normal hand feel method was not effective in this case for small items. I feel that only the dredge was able to recover the smallest of items in one day after a week of diving by normal methods failed to locate the ring.
Diving a recovery of a crash site is a large undertaking and forces many factors into play. The initial recovery of the victims and aircraft is a priority and is done to bring the initial closure to the victim’s family. Investigation of the crash is always in the planning and documentation of the recovery and whatever actions you take will be brought into question later during the civil litigation that almost always follows a tragedy. The ability of the dive team to fully search a crash site to the degree that satisfies any investigator’s or attorney’s questions will be tested with each dive. While the supervisor must contend with the many issues at a dive, the one factor that influences every action will be cost. A large scale search is costly in man-hours alone. Divers and investigators multiplied by the hourly wages will push any recovery over several thousand dollars in a manner of days. A dredge can make possible the recovery of items that could be overlooked and cut the search time drastically, saving a department money at the same time.
After my supervisor observed that my makeshift dredge would take an hour to assemble and employ, wanted improvements made to eliminate this down time for the rest of the team. A local fabrication shop integrated the pump on top of new aluminum pontoons with the basket in the center. Two axles were placed under the pontoons so the entire system would roll off the trailer into the water, ready to work. This improved the dredge so that the next dive the cost of improvement was recouped in the first hour.
After two years of diving and experimentation we have learned many things that can be of use in the employment of a dredge in public safety diving. First, the dredge has it’s limitation like any other piece of equipment and its employment should be tailored to a search area for small items. Second, the dredge should be man portable and compact. Divers’ waiting for the assembly or movement of the dredge is money wasted by the department. I have a dedicated trailer and all parts of the dredge are assembled ready for use. I have altered a Keene Engineering five inch dredge to incorporate two wheeled axles and handles for transportation. The dredge can be easily carried by four people to cross fences or be transported by pontoon boat. The wheels allow one person to push the dredge across the ground or over mud and obstructions in the water. Third, the basket screen is half inch hardware cloth mesh to capture most evidence and inserts can be placed to recover smaller evidence such as bullets. Finally, below is a diagram and pictures of the dredge for illustration and its employment.
I hope this can empower department dive teams to have one more piece of equipment to accomplish its goal of evidence recover. Remember, it’s the dive team task to confirm or deny an item of evidence is a specified search area. That gives the investigator the confidence to question suspects or witnesses on the location of evidence. Often this will make the case a success or failure based on your ability to recover evidence.
Deputy Sheriff Brian Hanger can be contacted at [email protected]
Law Enforcement use of Dredges in Evidence Recovery
By Deputy Sheriff Brian Hanger
Polk County Sheriff’s Office (Florida)
The evolution of public safety diving for a majority of agencies has seen incremental but steady progress in the areas of equipment, training, and evidentiary procedures. Over the last twenty years, many agencies have progressed from small volunteer teams to specialized units within the department. Often these early teams consisted of members from a variety of backgrounds and provided their own equipment. Training was infrequent and employment of the teams was limited to the recovery of objects that were discernable by touch. The classic “grope on a rope” is still a viable search technique but is often limited due to bottom conditions and size of the object. This article will examine the use of small dredges in the recovery of evidence by public safety dive teams as an additional method in evidence recovery.
As a member of the Polk County Sheriff’s Office (Florida) underwater search and recovery team (USART) for the past eleven years, I have witnessed my own team’s transformation from a basic volunteer organization to a capable specialized unit. My beginning experience as a new diver with USART was showing up for my first dive with my personal gear to a nearby lake and searching for a stolen vehicle in the water. After a series of rope sweeps I collided with a large immovable object that I determined to be the vehicle. A majority of Central Florida water bodies have zero or close to zero visibility forcing the diver to use their imagination when encountering an object. The general rule for divers was to return to the surface with any object they thought was the search item or mark anything too large to move with a buoy or rope. This works well for large objects like stolen vehicles. The difficulty starts when the search item(s) are small.
My next dive was an evidence dive for the homicide unit. A man was suspected of shooting his wife with a small caliber handgun. The suspect denied involvement in the crime and detectives where unable to locate the murder weapon. After a series of interviews with associates of the suspect, detectives learned of an incident in which the suspect and a friend were target shooting into a local canal. The friend of the suspect described the suspect using a handgun of the same caliber as the murder weapon and was willing to testify to the incident. Homicide detectives then called the dive team to search the canal for spent bullets for comparison to the bullets recovered from the victim’s body. A match would give the detectives a solid case.
Upon arrival the dive team set up a standard rope search and equipped the divers with underwater metal detectors. The search barely progressed a foot when the diver stopped to recover a signal from the metal detector. After several moments a fishing weight was recovered. The search began again and another foot of progress recovered pull tabs and fish hooks. The third foot searched revealed numerous 45 caliber bullets which where not the caliber we were searching for. An hour of searching had covered approximately ten square feet of lake bottom next to the shore and a growing pile of trash. Detectives watched the painfully slow progress and made a mental calculation that the potential search area of a bullet trajectory could be huge. A decision was made to search the immediate area next to the shore out to 60 feet. The dive continued to produce large amounts of trash and other incorrect size bullets. At about twenty feet from shore the divers encountered the beginnings of a deep silt layer that was over the reach of the diver’s arm. Metal probes were used to find the lime rock layer under six feet of silt. This prevented the metal detector signal from reaching any bullets that had penetrated the silt or hand excavation by the divers. With this information passed to the detectives it was determined that we could not discount or prove the suspect fired the murder weapon into the canal. This dead end started the search for a new method of small evidence recovery.
In my search for a new method of small evidence recovery I began searching the internet for equipment use to find small objects in the water. The most similar concept I found to evidence recovery was recreational gold dredging. Recreational gold dredging relies on the venturi principle; water passing through one side of a forked pipe will draw suction on the other side of the fork. With a hose attached to the suction side of the pipe a person could then draw the material through the hose and pipe and have the contents deposited in a basket. This method would accomplish my needs of moving material in such a way as not to damage evidence by passing items through a pump. The basket would be substantially different than a gold dredge so that a majority of the sand would fall through the screen and leave whatever size item the screen was designed to hold. Gold dredges must process this sand through a riffle system to find gold dust and small nuggets in the sand. My needs were for a system that would only hold the size item I was looking for and quickly pass the silt and sand back to the bottom. With a few modifications I believed I had the answer I was looking for.
I decided on a personal purchase of equipment from Keene engineering in California and built a somewhat makeshift dredge to begin experimenting on evidence recovery. The motor and three inch trash pump was placed in a small aluminum Jon boat connected to the water intake and venturi pipe. The silt and debris was pumped through the venturi pipe into a floating basket approximately four foot long and two foot wide next to the boat. The floats were made from eight inch PVC pipe capped at each end and tied with rope to the basket. This entire set-up would be put to the test soon after completion.
The dive team received a call for assistance from a local law enforcement agency to search for a handgun used in a shooting from a local lake. The lake is in the center of town and has over a hundred years of run off from the city streets drained into the lake. We set divers in a normal rope search pattern from the shore at the point the detectives believed the gun was thrown. The first several feet was covered in bottles and trash and was removed by hand. At approximately fifteen feet from shore, the silt was over the arm of the divers. Sixty feet from shore, the water was six feet deep and the silt was still over the reach of a diver’s arm. This would be the first real test of the dredge. The next day the dredge and boat was set up and a pattern was begun from shore. The first problem realized was that a three inch hose would not pass the average bottle or can. This lead to numerous stoppages in order to clear the vacuum hose of obstructions. We underestimated the sheer volume of bottle and cans that had accumulated in the downtown lake. Bottles and cans in the hundreds were encountered with silt over seventeen feet as we dredged into the lake. I came to the conclusion that a small three inch pump powered by a five horsepower motor was not up to the task for the volume of material that need to be searched. We now currently use a five inch dredge that can pass bottles and can to the basket and can be removed by the topside tender(s) and allow the diver to remove the maximum amount of material.
One concern that was raised by the city parks and lakes manager was the issue of water quality as the result of dredge usage. A previous meeting with the state Department of Environmental Protection and Southwest Florida Water Management District had been conducted to address water quality and permitting issues. Both the DEP and SWFMD agreed that we would be exempt from permitting based on the infrequent use, use by a law enforcement agency and we would inform them of times and places where the dredge would be operated. The city parks and lakes manager was also helpful in documenting the limited area of turbulence from the dredge. Our experience is that the dredge used in lakes and streams will create a turbulence area similar to that of a rainstorm runoff in an area approximately thirty feet in diameter. Generally material lifted from the bottom will return to the bottom in a short time.
Our agency experienced a tragic loss when a department helicopter crashed in a phosphate mine reclamaintion lake killing two of our members. The dive team responded and conducted the initial recovery of the pilot and co-pilot along with the main fuselage of the aircraft. After several days of diving to recover smaller fragments of the aircraft for the crash investigation, we received a request from the pilot’s wife to recover his wedding ring. The dredge was employed at the crash site and recovery of numerous fragments of the aircraft and personal effects began. The ring was recovered along with every bullet assigned to the officers as well as gauges and other items of evidence.
Investigation of aircraft crashes relieves heavily on the recovery of gauges due to the effect of “needle slap” on the gauge at the moment of impact. The investigator can determine the aircraft’s engine, flight, and mechanical status leading up to the crash. Every part of the aircraft recovered can be tested for metal fatigue, placement or pre-crash damage to give a more complete analysis of the accident. One missing piece of the aircraft can give rise to a legal question of doubt in the enviable civil litigation. The most complete recovery possible will be the standard dive teams are held accountable.
This recovery was done after a week of diving by our dive team and Orange County Sheriff’s Office dive team. Divers were faced with zero visibility water along with heavy vegetation and the normal hand feel method was not effective in this case for small items. I feel that only the dredge was able to recover the smallest of items in one day after a week of diving by normal methods failed to locate the ring.
Diving a recovery of a crash site is a large undertaking and forces many factors into play. The initial recovery of the victims and aircraft is a priority and is done to bring the initial closure to the victim’s family. Investigation of the crash is always in the planning and documentation of the recovery and whatever actions you take will be brought into question later during the civil litigation that almost always follows a tragedy. The ability of the dive team to fully search a crash site to the degree that satisfies any investigator’s or attorney’s questions will be tested with each dive. While the supervisor must contend with the many issues at a dive, the one factor that influences every action will be cost. A large scale search is costly in man-hours alone. Divers and investigators multiplied by the hourly wages will push any recovery over several thousand dollars in a manner of days. A dredge can make possible the recovery of items that could be overlooked and cut the search time drastically, saving a department money at the same time.
After my supervisor observed that my makeshift dredge would take an hour to assemble and employ, wanted improvements made to eliminate this down time for the rest of the team. A local fabrication shop integrated the pump on top of new aluminum pontoons with the basket in the center. Two axles were placed under the pontoons so the entire system would roll off the trailer into the water, ready to work. This improved the dredge so that the next dive the cost of improvement was recouped in the first hour.
After two years of diving and experimentation we have learned many things that can be of use in the employment of a dredge in public safety diving. First, the dredge has it’s limitation like any other piece of equipment and its employment should be tailored to a search area for small items. Second, the dredge should be man portable and compact. Divers’ waiting for the assembly or movement of the dredge is money wasted by the department. I have a dedicated trailer and all parts of the dredge are assembled ready for use. I have altered a Keene Engineering five inch dredge to incorporate two wheeled axles and handles for transportation. The dredge can be easily carried by four people to cross fences or be transported by pontoon boat. The wheels allow one person to push the dredge across the ground or over mud and obstructions in the water. Third, the basket screen is half inch hardware cloth mesh to capture most evidence and inserts can be placed to recover smaller evidence such as bullets. Finally, below is a diagram and pictures of the dredge for illustration and its employment.
I hope this can empower department dive teams to have one more piece of equipment to accomplish its goal of evidence recover. Remember, it’s the dive team task to confirm or deny an item of evidence is a specified search area. That gives the investigator the confidence to question suspects or witnesses on the location of evidence. Often this will make the case a success or failure based on your ability to recover evidence.
Deputy Sheriff Brian Hanger can be contacted at [email protected]
