3rd Leuchter Report


The function of a Lethal Gas Chamber is simple in theory, but complex in actual usage. Essentially, the executee is sealed into a chamber which is inwardly pressurized (evacuated) causing any leak of dangerous hydrogen cyanide gas to be inward. By means of an external actuator, sodium cyanide pellets (briquets) are dropped into warm, dilute sulfuric acid within the chamber. Hydrogen Cyanide (Zyklon B) gas is generated within the chamber due to the chemical reaction of the sodium cyanide and the sulfuric acid. The released gas surrounds the executee and terminates his life.

After a sufficient time has elapsed, the chamber is ventilated completely, with air in excess of 80 degrees Fahrenheit, many times over, and the subject is removed after proper neutralization with ammonia. The prussic acid, residual to the chemical reaction, must be disposed of. The Chamber must be neutralized by washing with ammonia and caustic soda or chlorine bleach. Care must be taken in handling the corpse, cleaning the chamber and gas generator, and evacuating the gas to see that no one other than the executee is killed.

7.001 The Mississippi Lethal Gas Chamber is operated in the following manner. First, it is tested to determine if all of the plumbing is clear and tight. This is done by opening Inlet Valve (3) and Outlet Valve (4) and running tap water into the Acid Mixing Pot (9) for five minutes. This determines that there are no blockages in the plumbing. Then Valve (4) is closed and tap water is run into the Acid Mixing Pot filling the Gas Generator (D) to the floor level of the lethal chamber. The piping in the pit is then inspected to determine that there are no leaks. The Gas generator Valve (1) is then closed by utilizing Gas Valve Lever (1), trapping the water above the valve at floor level. Then, Outlet Valve (4) is opened, allowing the water to drain into the sewer, since Gas Valve Lever (1) has opened the Gas Generator Vent Stack Valve (A).

7.002 Next is the vacuum test. First, check the Packing Gland and tighten the window frames onto the gaskets. Close and seal the door. Then place some water around Air Intake Valve (2) (to ensure a tight seal) and close Valve (2) by actuating Lever (2). Open Air Exhaust Valve (5) by means of Fan Damper Lever (5) and start exhaust Fan. This will pull a vacuum on the chamber. We must now monitor the Manometer (6) to determine if it remains constant or indicates there is a leak. If there is no leak, the following is done to effect an execution: turn off fan and open the Air Intake Valve (2). This relieves the vacuum. Open the door. The heat must be turned on and the Death House brought to and maintained at a temperature of over 80 degrees Fahrenheit to prevent condensation of the hydrocyanic acid on the interior of the gas chamber, which would make cleanup extremely dangerous. Hydrogen cyanide gas condenses at 78.3 degrees Fahrenheit (25.7 degrees Celsius) and the intake air in the control room must be kept above this temperature.

7.003 Utilizing the Gas Valve Lever (1), the Gas Generator Valve (10) should be opened and closed to eliminate any water trapped above the floor in the last test. The Sodium Cyanide briquet container above the valve should be thoroughly dried so that no moisture will reach the cyanide briquets until the execution begins. The door gasket, the window frames, the Packing Gland, the Manometer inlet, and the two heart monitor connections are coated with petroleum jelly as a guard against leakage. Two or more gallons of distilled water are poured into the system to insure that traps # 1 and # 2 are full. All chemicals (acid and water as well as caustic soda) are mixed and readied.

Outlet Valve (4) should be closed to seal the system from the drain, and Intake Valve (3) should be closed to contain the acid/water mixture until ready. The Gas Generator Valve (10) should be verifies as closed and the locking pin installed through the hole in the Gas Valve Lever. The sodium cyanide briquets should now be placed in the briquet container above the valve. The Acid should be mixed with warm distilled water and placed in Acid Mixing Pot (9). Air Intake Valve (2) should be closed. The Ammonia Injectors should be made ready by closing the Injector Valves and by pumping up the pressure. The watch-glass of Phenolphthalein solution is placed on the shelf within the chamber. The doctor tapes the mechanical stethoscope and the electronic heart monitor to the executee's chest. The door is closed and sealed.

The doctor verifies that the two heart monitors are working. The Air Exhaust Valve (5) should be closed and the Exhaust fan should be started. The vacuum should be monitored on the Manometer (6). Inlet Valve (3) should be opened allowing the acid/water mixture into the gas generator, and then closed. The Acid Mixing Pot (9) should be completely filled with tap water to prevent backflow of gas. The Lethal Chamber is now ready for the execution.

7.004 The Emergency exhaust fans are now verified as operational. A monitor is stationed at the Manometer. A monitor is at each chamber window, Air Intake Valve (20, and the chamber door with a hand held gas detector which sense Hydrogen Cyanide Gas to 10 ppm (parts per million). The emergency breathing apparatus (air packs) are verified as being immediately available to those present in the Death House. The execution can now proceed. The manometer (vacuum) is verbally verified and Air Intake Valve (2) is visually verified as closed. Additionally, special hydrogen cyanide first-aid kits are on hand in the Death House, special emergency physician's medical kits and two resuscitators are on hand at the infirmary, and two emergency ambulances are on standby inside the prison. The guard tower at the entrance sally port of the Maximum Security Facility is evacuated as a precaution against wind carrying the expelled air-gas mixture to the tower and killing the guard stationed there. This is the only time that this most important security post is abandoned.

7.005 On command from the Warden, the execution is begun and the witness curtains opened. The locking pin is now removed from the Gas Valve Lever and the Gas Valve Lever (1) is thrown, opening the Gas Generator Valve (10) which drops the cyanide pellets into the acid solution beginning the generation of the gas. The monitors verify that the vacuum is holding and that there are no leaks detected. After several minutes, the executee will be dead and the doctor will verify this fact. The doctor will wait several more minutes and inform the Warden that the subject is dead. (Total time normally ten [10] minutes.) The Warden will then order the chamber to be cleared of gas and the witness curtains closed.

7.006 The Gas Valve Lever (1) will be returned to closed position which will close the Gas Generator Valve (10) (which will prevent any further gas from entering the chamber) and open the Gas Generator Vent Stack Valve (A) preparing the Gas Generator for draining. The Fan Damper Lever will be thrown, opening the Air Exhaust Valve (5). The Air Intake Valve (2) will be opened and the Manifold Ammonia Valve (7) opened. The Chamber will begin exhausting the air/gas mixture and the ammonia will begin to neutralize the hydrogen cyanide and protect against any leakage back through the Air Intake Valve (2). The Chamber will be cleared (according to tests) in one minute (Eaton says three). This exhaust procedure will continue for fifteen (15) minutes (at Eaton's instruction) to guarantee at least five full air changes.

Open Outlet Valve (4) allowing the prussic acid residue to pass into the sewer. Open Inlet Valve (3) allowing water in Acid Mixing Pot (9) to pass into the plumbing and flush the system while opening Ammonia Injector Valve (8) to insure no back-flow of poison gas. Pour Caustic Soda solution into Acid Mixing Pot (9) and flush continuously with tap water for fifteen minutes or more. Both Ammonia Injectors (Valves 7 and 8) should be turned off in ten (10) minutes.

7.007 After at least fifteen minutes of venting the chamber, the phenolphthalein solution should be checked for its characteristic red color, indicating that the chamber is clear. When the chamber is clear, two operators, wearing full chemical suits with air-packs and rubber gloves, will open the chamber and verify with gas detectors. (Previously, gas masks with hydrocyanic acid and ammonia were utilized.) The operators in the chemical suits ruffle the executee's hair to eliminate any trapped gas and then spray the executee and the chamber with ammonia. The doctor, now wearing a chemical suit with an air-pack, makes the final pronouncement of death.

The executee is now undressed and washed with a caustic soda or ammonia solution and is removed from the chamber and redressed in different clothing. His body is then ready for removal by the undertaker, who works on the body thereafter, with rubber gloves. The clothing worn by the executee at the time of execution is placed in a plastic bag and sealed, after which it is disposed of, generally by incineration.

The Gas Generator Valve (10) is now opened by throwing Gas Valve Lever (1). The Lethal Chamber and all its contents are washed with caustic soda (walls, floor and ceiling) and the residue flushed into the Gas Generator at the base of the chamber and thence down the drain. Gas Generator Valve (10) is then closed by throwing Gas Valve Lever (1) and the plumbing continuously flushed for another ten (10) minutes. Upon completion of the cleanup, approximately an hour after the execution ended, the Death House is secured with the exhaust fan left running.

7.008 The following day, the step-down maintenance is performed. An inspection is made to determine if everything is dry. The fan is then turned off. The equipment is then stored in its proper place. All valves are closed and then opened to half position to eliminate pressure on the packing. The nuts on the window frames are loosened to eliminate pressure on the gaskets. The door to the chamber is left open so there is no pressure on the gasket. The Air Exhaust Valve will not be closed, to eliminate pressure on the gasket. The Death House is now made permanently secure.

7.009 Prior to the next usage, all valves will be checked, the window gaskets will be tightened and the Packing Gland will be re-packed. The Chamber will be again tested to the procedure outlined above.

7.010 The two man Lethal Gas Chambers built by Eaton were identical in design and construction to the one man chamber at Mississippi except that they had two seats and duplicate plumbing systems requiring that all chemical procedures had to be completed twice. Some of these chambers required that the cyanide pellets (often called "eggs") be placed in a gauze sack and dipped into the acid solution in the generator below the chamber by a trip mechanism similar to the one in Mississippi except that it was suspended from the chain instead of being fastened to the floor. This was changed because it was safer, in that no one had to handle the gauze sack after the execution.

7.011 The chemicals used by Mississippi are an approximate 37% Sulfuric Acid Solution (acid and distilled water) and an approximate 16 ounces of sodium cyanide. This requires twelve (12) pints of distilled water and six (6) pints of acid (98%) resulting in 18 pints of dilute sulfuric acid reacting with 24 briquets of sodium cyanide. This results in two (2) cubic feet of Hydrogen Cyanide gas at the 10 psi (approximate) operational pressure or an amount of approximately 7500 ppm.

Continue on to Design Criteria for a Lethal Gas Chamber or return to Leuchter Report Table of Contents