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This report has been prepared by
as a part of a Government Contract. The views expressed are those of personnel and not necessarily those of the United States Government.

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TABLE OF CONTENTS

Page
Prntocol Statement i
List of Figures and Tablea iii
Problem 1
Discussicn 1
I. Potential Applications 1
II. Paysical Variables of Electric Current 3
II. Paysiological Considerations 5
A. Effects of Electrical Current on Humans 5
B. The Human Body as an Electrical Conductor . . . 10
C. Skin Resistance .. 11
D. Burns and Other Thermal Injuries 12
E. Pulsed Current 13
F. Overcoming Skin Resistance 14
G. Path of Current Flow Through the Body 15.
H. Physiological Conclusions 17
IV. Other System Factors . 20
V. Equipment State of the Art . 23
VI. Recommendations 25
References 27

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LIST OF FIGURES

Page
Figure 1 Approximate Threshold of Heart Fibrillation
Hazard far Single Brief Current Surges
(AC or DC) ..
9
Figure 2 Diagram of Body Area Combinations for Current
Flow Through Chest 17

LIST OF TABLES

Table I Definition of Basic Electricity Terms
3
Table II Sensation,and Effects on Heart and Respiratory
Muscles of Currents Lasting 1 to 30
Seconds
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ELECTRIC CURRENTASANAGENT FOR PERSONNEL INCAPACITATION.

PROBLEM

To evaluate, especially from the physiologic point of view, electric current as an agent for personnel incapacitation.

DISCUSSION

I. Potential Applications for Incapacitation

Electric current possesses a number of possible advantages when compared .to other proposed agents for personnel incapacitation. Controlled electric shock offers, not necessarily simultaneously, the following possibilities:

Broad spectrnm of incapacitation: annoyance, fear, intimidation, pain, muscle spasm, mincr burns, paralysis, suffocaticn, unconsciousness, severe burns, death.

Relative predictability of physiologic effect: reliable relationahip between dose and responses.

Contro.lability: of dose and on/off times.

Directivity: with respect to person to be incapacitated and body part(s) to be affected.

Effectivencss on a wide range of subjects: regardless of determination or level of consciousness.

Rapidity of incapacitation: onset of action within a second.

Rapidlity oi recovery: only a fow seconds for the milder effects.

Safetyi for both the operator and the subject,\* if desired.

Throughout tr,s report, subjects are assumed to be healihy, adult humans in the 45 to 90 kilogram weight range.

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Covertness: quiet and unobtrusive, can be camoullaged.

Aside from technical details of the delivery system, the only broad limitations to use of clectric current as an iucapacitation agent have to do with the number of subjects and the duration of incapacitation. It is difficult to conceive of realistic circumstances that would perrrit a safe and uniform dose to be administered to a number of subjects at one time, although current would be as effective for the entire group as it is for an individual. In this report, current is considered as an incapacitating agent for individuals only. Electric current can be quite safe for periods of incapacitation of a few seconds only; hazards become much greater if current is used to maintain incapacitation for a minute or longer, unless special techniques and precautions are used,

Within these limitations, current could be used as an incapacitating agent under virtually any circumstances. Power can be supplied from permanent supply lines, temporary generators and lines, or po=table supplies (including pocket-sised battery packs in some cases). Delivery systems might be permanent installations, temporary traps, hand-held instruments or longrange projectile devices. Automatic controls would suffice for systems designed for brief incapacitations, but systems maintaining incapacitation for more than a few seconds should be controlled by an operator who has aome training in the methods of safeguarding the hea'th of the subject.

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The performance and suitability of electric shock for personnel incapacitation may be affected by several variables which characterize the incapacitating current. The more important elcctrical parameters are voltage. current, power (or energy) and frequency. For familiarity, these and other terms used in this study are briefly defined in Table I.

II. Physical Variables of Electric Curront

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Electric currents are most often supplied (rom batterics (direet cur ent) or from rotating generators (either alternating or direct currenl). The current is usually carricd from one locale to another hy low resistance conductors, such as non-ferrous metals, or by ionizcd liquids or gascs, and is prcvented from leaving the desirad path by high resistance insulators. The application of current or voltage to basic electricat devices, including resistors, coils, and capacitors, permits a wide range of functions to be performed by electricity. These basic electrical devices conpled with more complicated devices. such as vacuum tubes and transistors, form the working components of all electrical and elertronic sysiems which generate, transmit, store, amplify, modulate or otherwise control electrir: eurrent.

Purposeful control of the variables of electricity can be accomplished through the use of these basic devices. For example, a coil or inductor will tend to conduct direct current and low frequency alternating current. while impecing high frequeney alternating current. Similarly, a capacitor or condenser acts as a conductor for high frequency alternating current, but impedes direct current and low frequency alternating current,

The spectrum of physical and physiological effects produced by the variations of volrage, current and frequency is probably familiar to many readers: the tingle of a mild electric shock of low amperage, the appearance of a high voltage arc discharge, the accidental burn from l10 volt, 60-Hertz 'house current" or the painful shock from the high voltage of an automobile ignition system.

In terms of incapacitation and biological effects on living systems, current - not voltage - is the most irportant variable of clectricity. The frequency of the current may also be a factor in determining the deletericus effects of electric current, especially with regard to the sensitivity of the human heart.

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III. Physiological Considerations 25

A. Effects of Electrical Current on Humans

With thc exception of inconsequential effects such as the feeling of hairstanding-on-end, high voltages without current flow have no knowu effect on human well-being or performance. Polarity of a direct current or brief discharge makes no apparent difference with regard to the incapacitating effects of flowing current.

As it relates to the incapacitation problem, electric zurrent has only three significant effects on human tissues:

I. Depolarization of nerve and muscle tissue, causing the "firing" of nerve or brain cells and contraction of muscle fibers. Depolarization causes the subjective tingle, involuntary muscular contractions and several other side-effəcts of an electric shock.

2. Change in sensitivity of certain irritable tissues, such as increased heart irritability and sensiti ity to fibrillation.† Fib-illation is an uncoordinated "bag-of-worms" contractile activity of the heart, and is a major threat to life which may ensue when moderate electrical currents pass through the heart. Death can follow because a fibrillating hsart cannot pump blood.

3. Heating, to the point of coagulation and burnit.g if current flow is Iarge enough or concentrated in a small area.

All three of the above effects could contribute to the pain of a severe shock, although a large part may be pain due to muscle spasm. ★

Unless otherwise attributed, the material presented in this section is derived from Rererence l, which also provides a bibliography of the basic publications on the physiologic effects of electric current.

In this report, fibrillation means ventricular fibrillation.

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Detailed cffects can be predicted if the arrperage. route through the body. duration of current flow and frequency of the powe: supply are known. Delibcrate exccution in an electric chair is an extreme example in which approximately 10 amperes of 50 to 60 Hertz current are passed from hcad to both feet for longer than a minute. Such a lethal current causes immediate unconsciousness; immediate and continuous "tetanic" contraction of all major muscles including the heart, thereby arresting respiration and all useful heart activity, and severe heating effects most pronounced where the pcial electrodes make contact with the skin. The colloquial phrase "frying in the chair" seems apt.

A less drastic but equally dramatic,.e of electric current is in electroconvulsive therapy or "shock treatment" for mental iliness. In this case. 50 to 60 hertz cuxrents on the order f l ampere are passed from one side of the head to the other for one-half second or less. 2 The patient immediately toses consciousness and has a generalized convulsion that afpears to last longer than the duration of current application. The patient usually regains corsciousness within a few minutes and may be physically able to walk promptly. There is likely to be residual muscular soreness and a confusional state may persist for any period of time from seconds to days. The patient retains pexmanert amnesia for the time of the shock and usually makes no serious objection to repeat treatments. Therapy personnel take great care to riake large-area, low-resistance electrical contact on both sides of the head to prevent current burns on the patisnt's scalp. It must be emphasized that cur-ent flow, and hence all direct effect, of electroconvulsive therapy. is confined to the head. The depolarizing action of the current on the brain causes convulsive stimuli to flow out to the muscles through the normal channels of the nervous systemi there is no significant current flow through the trunk or extrcmities although they move violently. Only organs in the path of the current flow can be affected directly. This is why there is no risk of direct electrical interference with heart action during properly conducted electro-convulsive therapy.

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Crrents passing through the torso can cause spas:ic paralysis of the respiratory, back and abdominal musc!cs. Continuous paralysis of the respiratory muscles fur several minutes can lead :o suffocation regardloss of other consequences. The most immediate and potentially lethal threat posed by a zurrent passing through the chest, however. is electrical interforence with heart activity. Table I outlincs the hazards of currents appled externally to the chest for several seconds.

Inspection of Table Il reveals several key points, For a given currcnt level in the 0 to 3, O00 milliarpere range, alternating current has greater physiologic effect and is more has,ardous than direct current. Fibrillation of the heart is rarely caused by direct current regardless uf amperage. Ventricular fibrillation is almost always fatal unless given special treatment within minutes. but hearts that have been completely paralyzed for short periods usually resume normal activity spontaneously after the current stops. This difference accounts for the apparent paradox in the doseresponse relationships shown for alternating currents: othex factors being equal, a current greater than 3 amperes is less likely to be immediately fatal than currenta in the 80 milliampere to 3 ampere range. It must be emphasized that the approxirmations indicated by Table II are valid only for curreut applied externally across the chest and for the indicated durations. The voltage required to produce a given current, cf course, is highly dependent on the nature of the electrodes, skin resistance, and oiher factors.

The fibrillation threshold rises for current durations shorter than one seeond, at least for non-repetitive pulses of curreut. Figure l indicates an approximate "worst case .hroshold for fibrillation hazard in terms of the current-time factor for brief exposures to any type of current. including 60 Hz AC and capacitor discharges. For shocks lasting less than one second, the thresho.d shown by Figure 1 is for constant energy pulscs of 1.6 joulc

\* The stardard method of "closed" defibrillation :s to apply about 300 joules of electrical energy in 0.2 scconds or less through large electrodes held firmly on the skin of the anterior cbeat.1 One joule is one watt-secoud.

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each, Sovcral authorities suggest that hazard threshold might well be at
energy levels an order of magnitude higher than that showni thus the thres-1
hold shown by Figure I may he quite conservative.

Currents of sufficient magnitude will cause painfu! involuntary contraction of muscles as the currents pass through an extremity. The motion made by the extremity as the muscles contract will depend upon: (l) the muscle groups stimulated, and (2) the relative strengths of contraction of the various muscle groups. A person "thrown' or "knocked down" by electric shock has been moved by his own muscle contract\_ons rather than any direct propulsive effect of the current. Relatively weak movements caused by stnall currents can be overcome by voluntary muscle control, especially in large powerful people. A "no-let-go" current threshold can be determined by measuring progressively larger currents flowing through a person's arm from an electrode grasped in his hand, up to the current at which he can no longer voluntarily release the electrode with the current flowing. The no-let-go threshold for adults is in the 6 to 3C milliampere range for 60 Hz AC. Current values will be similar for other AC frequencies in the l0 to 1, O0o Hz range, but DC currents would have to be about five times as

B. The Human Body as an Electrical Conductor

From the standpoint of electrical shock, the normal human body can be considered as a bony framework encased in a protein gel with some lipids. all of which is permeated with an aqueous salt solutioa and encased in a waterproof skin, The electrical resistance of organs generally varies inversely with water content, Tissues zuch as blood and muscle display resistances in the order of I, O00 ohms per cubic centimeter while dense bone, fat and nervous tissues have resistances several tires higher. Wholc body resistance. exclusive of skin, is on the order of 200-1,000 ohms. The trunk has a lower resistance than the extremities with their smaller cross section and high proportion of bone. Current inside the body appears to spread in a

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fairly uniform manncr through the available volume bctween the point of entrance and tho point of exit rather than being noticeably concentrated along any special low-resistance path.

The skin usually presents the major resistive barrier to electric current flow. Most sf the skin resistance is in the cpidcrmis, the dry, horny outer layer without blood vessels. Thickness of the epidermis, and hence the resistance of the skin, may vary widely between different parts of the body. Thin skin behind the knee or in the axilla may offer less than a thousand ohms resistance, especially if moist. At the other extreme, a thick, dry callous may offer resistance approaching a million shms. Skin that is relatively moist, such as on the palms, soles or axillae, will be more conductive than drier skin of the same thickness elsewhere on the body.1 During sound sleep, all skin resistance rises greatly. 4

C. Skin Resistance

The major factors in electrode-to-body resistance through the skin are:

1. Thickness and intrinsic moisture of the skin, as noted above. Range: about 1,000 - 1,000,000 chms (dry contact)-

2. "Wet" or dry contact. Presence or absence of an electrolyte solution providing a conductive pathway between electrode and skin. "Wet" contact can be proveded by special preparations such as electrode paste or fluids such as sweat, blood, saline solution or even tapwater. Conversion from a dry contact to a "wct" one usually drops the -esistance one or two orders of magnitude.

3. Intact or damaged skin. Any thinning, scratching or penetration of the epidcrmis can drastically reduce skin resistance. In addition to any reduction due to a wet contact, painless, gentle sandpapering of the skin can also reduce the resistance one or two orders of magnitude. Even a tiny penetrating burn, such as that caused by a small area of contact with high voltage, will cause a near-instantaneous drop ia skin resistance to a

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few hundred ohms or less.

4. Area of contact. Other factors being cqual, resistance is inversely proportional :o the area of contact. A large area of uniforn dry contact is difficult to achieve in practice. Significant and predictable reduction in rosistance by large area contact is ordinarily achieved only with wet contact such as immersion of a body part or wet clothing.

5. Pressure of contact. Increased pressure on a dry contact with intact skin can reduce resistance, but the effect is usually not pronounced enough to cause dxy electrode-to-skin resistances lower than 10, 000 ohms until the contact pressure exceeds 10 kilograms per square centimeter.

6. Frequency of the electric power. Skin impedence, or total tendency to obstruct the flow of electric current, is inversely proportional to increases in the frequency of the applied electric power. The relationship is not sufficient to lower the effective skin impedance two orders of magnitude until the power supply frequency approaches l00 kHz. This report is not concerned with such radio frequency currents because "skin effect". keeps most of the current on the body surface where it is ineffective as an incapacitating agent.

7. Skin covering. Dry hair and most dry clothing can increase the electrode-to-body resistance by millions of ohms.

D. Burns and Other Thermal Iniuries

The heating effects of electric current are dependent upon the amount of electrical ene-gy being dissipated per unit time in a given volume of conductor. About four joules of electrical energy must be dissipated in a gram of water in order to heat the water one degree centigrade. In general, the temperature rise of tissue being heated by electric current varies:

1) directly with the square of the current

2) directly with the resistance of the tissue

3) directly with the time of current flow

4) inversely with the effective volume or cross-section of the conductor

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Consideration of these facts leads to the conclusion that the highest temperature rises in most cases of clectrical shock will occur in the skin at one or both points of electrical contact with the body. For significant current flows, skin burns of some degree will rcnain a hazard unless special precautions are taken to avoid high skin rèsistance and small cffective cross-sections of clectrical contact with the skin.

Conversely, the large effective cross-section and low resistance of the body beneath the skin means that many amperes of current flowing for prolonged periods would usually be required to "cook" organs other than the skin.

An electric arc in air at one atmosphere has a temperature of 2500° to
3000° C and can cause local heat effects other than those due to current 1
passing through skin resistance.

E. Pulsed Current

Repeated brief pulses would seem to offer several decided advantages as a . form of deliverirg electrical energy for incapacitation purposes. At a pulse repetition rate of one per second or faster, pulsed currents should be able to cause as much pain, paralysis and incoordination as continuous current, perhaps even more than continuous direct current. Very brief pulses and a small duty cycle would mean low average power levels, resulting in: (1) reduced burn hazard to the subject; and (2) reduced drain on the power supply system. For example, a one ampere pulse lasting one millisecond (0.25 joule of energy, assuming internal body resistance of 250 ohms) cculd be repeated at 10 pulses per second with a time-average power of only 2.5 watts, one hundred times less than a continuous current of one ampere. If such pulses passed through major portions of a man's body, they should be completely incapacitating with only minor burn hazard and low drain on the power supply. Figure l might be misconstrued to suggest that such a pulsed current is known to be safe as far as the heart is concerned. It must be emphasized that the figure relates to a single

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non-repetitive pulse only, and that hazard thresho:is t» peated pulscs remain to be determined.

Working with data from studies using humans and experimental animals, Zoll and cc-workers found that: (1) 3 millisecond pulses of about 100 miiliamperes (energy 0.06 joule and less) applied across the chest would trigger a heartbeat; and (2) pulses repeated 8 to 2) times per second for 5 periods on the order of a minute could cause fibrillation in some cases. Thus a one ampere pulse lasting one millisecond (energy 0.25 joule) would be likely to trigger a heartbeat each time the pulse passed through the chest, and a fibrillation hazard could exist in normal hearts subjected to rapid rates of such "extexna! heart pacing" for prolonged periods. From the information presented by Zoll et al, there woutd appear to be little danger of fibrillation or low cardiac output if the external pacing is carried out al a rate within the normal heartbeat range. Thus a repetition rate of about two pulses per second might prove to be well tolerated for prolonged periods, at least as far as direct cardiovascular hazard is concerned.

Incapacitazing pulses passing through the chest at a rate of about two per second are likely to interfere seriously with breathing, and might prevent loud vocalization, along with any other coordinated action. If breathing were stopped by the pulses, the subject could eventually suffocate,

The safety of repeated brief pulses for incapacitation purposes has not been report dated 25 June 1971. proved by the The longest reported test period was four seconds and no evidence is presented with regard to the subjects'cardiac or respiratory status during the test period, the time required for functionai recovery after delivery of the last pulse, and the thresholds for "no-let-go" status and skin burus.

F. Overcoming Skin Resistance

As previously noted, hurnan skin and hair often present a major resistive

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barricr to delivery of electric current for incapacitation purposes. Methods of overcoming the skin resistance problem may be summarized as follows:

Avoid the skin. Make contact with moist mucosal surfaces such as mouth and rectum.

Use wet skin, Make contact with skin surfaces that are alrcady wet, or dcliberately moisten the electrode placement sites.

Use damaged skin. Make wet contact with skin previously or deliberately scraichcd or abraded, as with an abrasive electrode paste.

Penetrate epidermis with electrodes. Make direct contact with structures beneath the epidermis by means of electroces in such forms as needles, splinters, burrs and slivers.

Use high voitage. Sufficiently high voltages will force any required cuzrent through the skin regardless of high skin resistance. High voltage cannot be considered a simple all-purposed solution to the skin resistance problem because high voltage is likely to cause extremely rapid changes in skin characteristics. A voltage high enough to force an incapacitating current through two high resistance dry skin contacts may well cause small burns that result in a drastic fall in skin resistance; if high voitage is maintained in :he face of rapidly declining resistance, an enormous and hazard. ous current flow develops. Various electrical techniques are available to limit current flow in such cases. Use of high voltages also requires that special precautions be taken to avoid short circuits that bypass the subject's body.

G. Path of Current Flow Through the Body

The complete loop of current flow must be considered in every case of electric shock, and any changes taking place during the shocking process must be borne in mind. The locations of effective current entry and exit from the body are all important with regard to physiologic effect, considering that current has direct effects on onty those organs through which it flows.

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Two electrodes closely spaced. Currcnt entry and exit points within a few centimcters of each other on the body surface can cause local pain, muscle spasm and burns only. The only significant exceprion woutd be electrodes on the front of the chest where part of the current could flow through the heart. Closely spaced electrodes could be uscd to cause limited incapacitation by pain and, if properly used, could be quite safe.

Two electrodes widely spaced. Widely spaced electrodes on the body surface offer a great variety of possible physiologic consequences. depending on ful: details of the method used. In all cases, there will be tocal effects near the electrodes as noted above. Large currents passing between electrodes on opposite sides of the head may have effects similar to electroconvulsive therapy, at the risk of severe scalp burns unless the electrodes provide large arcas of good contact; similar effezts, along with others, might be expected with current flowing frorn the :op of the head to another electrode at neck level or lower on the body. Current flowing only in one extremity can have direct effects on that extremity only. There are many possibilities for widely spaced electrodes to cause significant current flow through the chest with resultant possibility of interference with cardiac and/ or respiratory activity. Figure 2 illustratea the possibilities of placement of contacts that cause a significant proportion of the current to flow through the chest. Electrode pairs offer such a possibility if they: (l) are on opposite sides of the plane AU; (2) are on opposite sides of the plane BC; er (3) are on the front and back of the chest or upper abdonen. Figure 2 shows that the only path from one extremity to another, not threatening chest activities, is from one lower extremity to another.

One electrode and "ground", This situation must be considered as two electrodes, the second electrode being whatever is considered "ground" in contact with both the subject's body and the other part of the essential closed circuit for current. The single electrode problem may be one thing if the subject is standing barefoot in a rice paddy, and entirely different if he is standing in dry sh' ≥s on a dry wooden floor. Any change in the subjcct's body contact with "ground," such as falling onto or away from "ground," can radically alter the current flow situation.

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H. Physiological Conclusions

It is possible to use electrical current as an agent to cause a whole spectrum of human insapacitation from minor distraction through muscle spasm. pain, contortion, minor burps, xespiratory arrest and perhaps vocal paralysis, cardiac arrest, unconsciousness with convulsion, severe burns and death.

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The approximate degree and duration of incapacitation can, within limits. be predetermined by appropriate selection of curren: type, amount, duration, and path in the body. In general, clectrical techniques tend to be time-limited if safety is a consideration; prolonged use of electric current to maintain incapacitation may present grave hazards to the subject in the form of burns, inadequate hcart output or inadequate respiration. On the other hand, a brief "knock-down" incapacitation can be achieved with relative safety by almost any large current flowing for an extremely short period of time (less than a millisecond).

Several techniques can be.used to increase the safety factor of current being used to incapacitate for longer than the "knock-down." A current large enough to cause extremely painful paralysis of the extrcmities presents no danger more serious than burns if it does not pass through the chest. In this respect, optimum safety with severely incapacitating currents could be achieved with the current flowing: (l) from one lower extremity to the otheri or (2) from a distal point to a proximal point on the same extremity. Over such paths continuous AC current of more than 25 milliamperes or DC currert of more than 80 milliamperes should keep at least one extrerity of a man painfully paralyzed for the duration of current flc; currents larger than an ampere could cause severe burns, especially if the current flows continuously for many seconds.

If the current path is through the chest, the use of direct current will virtually obviate the hazard of heart fibrillation although the likelihood of respiratory and cardiac arrest remains with direct eurrents in the effective range. Cardiac arrest causes unconsciousness within a few seconds and death after saveral minutes. Complete respiratory arrest usually causes unconscicusness in less than four minutes and death in about ten minutes. Both kinds of arrest would be likely with direct currents larger than 300 milliamperes passing through the chest, so incapacitating direct current would usually have to be kept in the 80 to 300 milliampere range if it is to be used for prolonged periods.

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The safety margin for incapacitating levels of alternating current flowing through the chest is narrow for periods as short as a few seconds and there is no margin of safety if the current flows for more than 30 seconds. All such shocks should be considered potentially lethal.

Carefully chosen pulsed currents, perhaps brief surgas of onc joule or less delivered once or twice per second, may offer effectivc and relatively safe incapacitation when flowing between any two widely spaced points on the body. Several key questions regarding the safety and effectiveness remain to be answered by direct investigation, but indirect evidence suggests that such pulses would offer the following advantages: (l) no direct threat to a normal heart for any duration of incapacitation; (2) only minor skin burns at worst; and (3) low average current requirement for the power supply. The facts remain to be verified, but such pulses passing from any point on the upper extremities or the upper body to any point below the waist may well be capable of preventing respiration and effective speech in addition to causing comp.ete immobilization by muscle spasm and pain. If this is the case, an operator could be equipped with a system enabling him to: (1) knock z subject down rapidly; (2) keep the subject incapacitated and un-- able to make an effective outcry for perhaps a minute; (3) turn the pulses off for long enough to allow the subject to take a breath or two: (4) turn the pulses tack on until the subject becomes blue or passes out; and (5) repeat steps 3 and 4 for a reasonable length of tirne. Properly handled, the subject should recover promptly after the pulses have been turned off for several seconds, and have no permanent ill effects aside from probable smallarea skin burns.

Electrical currents are not likely to cause the immediate coma and convulsion of eleetrc-convulsive therapy without: (l) severe burns about the head or (2) the use of techniques very similar to those used in EGT.

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IV. Other System Factors

A. Major Subsystems

Power Supply. Information presented in the preceding section of this report indicates that: (1) one large non-repetitive pulse lasting less than a second. might be appropriate as a "knockdown" technique; and (2) longer incapacitation wilt require continuous power in the i to 250 watt range, quite likely less than 25 watts, depending upon the technique. A large capacitor, previously charged from a primary source, could supply the sing!e brief burst of power. Systems requiring longer duration power could draw upon permanent supply installations, temporary generators, or batteries, as appropriate in terms of power drain and anticipated'duration. Power supply reliability should approach 100% in a properly designed system. Power conditioning equipment is needed to make the required changes, such as voltage step-up, temporary storage, current limitation, and modifications with respect to timing. The reliability of power conditioning equipment should alao approach 100%.

Controls. Excep: in special circumstances where sore degree of variability or automaticity of current delivery would be desirable, the current control mechanism probably should be a reliable manual on-off switch.

Delivery Conductors. Properly designed conductors should present few problems in systems where the electrical supply components and the electrodes have been prepositioned before the arrival of the subject, who is expected to move himself into appropriate contact with the electrodes. Similarly, ahort-range conductors, as for a hand-held device, should be quite rel:able. A conductor-propulsion combination suitable for swift long-range deployment will require extremely careful design if it is to be

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reliable with regard to open-circuit and short-circui: possibilitics under a variety of field conditions.

Electrodes. Electrode design and placement will have to allow for ali the variables to be presented by the subject and the ervironment in the field. The subjcct variables are likcly to include tocation in space. body posture, motion before receiving current, motion and posture after recciving current, clothing, moisture of skin and clothing, nature of surrounding objects proximity and actions of companions. Subject variability is likely to determine the path of current flow in the body of a subject who moves hirmself into contact with previously placed electrodes. Again, hand placement should be easy, but swift long-range placement af adequate electrodes will require expert design in order to be reliable under a variety of field conditions. Electrodes are subject to open-circuit and short-circuit failure modes, in addition to dangers or ineffectiveness which might result from inappropriate current pathways through the body.

B. Operator Risk

Standard electrical safety precautions, built into the system, should be adequate for operator safety so long as the operator avoids electrical contact with the electrodes or the subject white current is flowing. The operator could hardle the subject if he: (1) turned off the current; or (2) wore insulating gloves of an appropriate thickness.

C. Covertness

Aside from the actions of the subject, electrical current system activity should be inapparent to an observer except for the possible faint snapping noise, smell of ozone or burning and dim light o small high-voltage arcs. As discussed previously, the subject may or may not be able to scream, shout or signal. 'A severely incapacitated subject is likely to fall down, and might thrash about or jesk under some circumsiances.

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D. Courtermcasures

Only limited counterrmeasures would be available to protect a suhject from a properly designed electrical incapacitation system. In general, countermeasures wculd fall into the following categories:

Avoidance. Stay away from the electrodes.

Minimize current flow. Current penetration of the body can be effectively reduced by: (l) interposing an insulating layer between the electrode and the bodyi or (2) providing a low resistance shoxt-circuit path between electrodes so most of the current flow remains outside the body. Insulating footwear could often be a reliable countermeasure to any system using a single electrode with "ground," Insulating gloves might enabie a subject to remove electrodes delivering currents above the "no-let-go' threshoid if initial electrode placement does not provide a completely incapacitating path of current flow through the body. Protective clothing could have a low resistance (short-circuiting) outer layer and a high resistance (insulating) inner layer.

Interrupt current flow. Once a truly incapacitating current flow has been established in the subject's body. deliberate interruption of the current could be accomplished only by the operator or a third party coming to the aid of the subject.

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V. Eouipnicnt State-of-the-Art

The system is the cnly electrical incapacitation unit for which the authors of this report have detailed information. The 1 conccpt may be summarized as a self-contained, hand-carried, batterypowered unit designed to proiect one or two insu'ated delivery wires at high velocity to a subject who may be at ranges cp to l00 meters; delivery wire(s) may terminate at electrode(s) that may oe bare wire, net, dart. barb, burr. adhesive or some other form; current is passed through the subiect in brief 0. 1 to 3 joule pulses at about 30, 000 volts repeated 2 to 20 times per second. Data are presented from tests involving a small number of experimental animals and human volunteers. During these tests, inca-1 pacitation periods were limited-to four seconds or less.

In view of the information presented in this report, the concept appears basically sound provided that a reliable wire delivery and elec-, trode ernplacement system can be proved satisfactory under field conditions. From the physiological standpoint, safer and more rapid incapacitation might have been achieved with larger energy pulses repeated more slowly than the ten per second indicated in most of the tests. Available test information is not conclusive with regard to: (l) incidence of skin burns; (2) respiratory and vocal status during shocks; (3) whether or not personnel knew that they were "pacing" the hearts of the subjects; (4) effects of prolonged exposure to the pulses; and (5) results when electrodes are projected to the subjects rather than carefully taped in position.

Incomplete descriptions of other systems for incapacitation by electric current are also available. One is a patent application for a pistol that would produce 'artificial epilepsy" by firing a small projectile with two trailing wires, the projectile to be equipped with two forward-facing needle electrodes

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to penetrate the skin of the subject. The only way for such a device to cause a true generalized convulsion would be for the necdles to penetrate the subject's brain! Closely spaced electrodes can cause only local direct - effects. E:sewhere on the body, such a device could cause annoyance, pain and possibly burns before the subject removed the projectile.

Strcams of conductive fluid, such as impure water, have been suggested as alternatives to conventional metallic conducting wires and electrodes. Such suggestions have merit so long as practical considerations of range, time, and open-circuit and short-circuit problems are kept in mind.

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VI., Recommendations

1. Arrange to have necessary experimental work done in order to establish appropr.ate thresholds of effectiveness and safety for pulsed currents. The physiologic effects and hazards of selected pulsed currents could be substantially proved by appropriate observations with a small series of experimental animals. Common domestic animals, such as pigs, sheep. and calves that weigh about 70 kilograms, provide good models for adult men as far as electrical effects are concerned. Audio-cinematographic. electrocardiographic and pneumographic recording should be carried out with emphasis on the time of onset of apparently incapacitating muscular contraction, cardiac and respiratory status during incapacity, the recovery phase, and examination of the sites of electrode placement. Time-toincapacity, ability to make an outcry and time-to-recover would have to be investigated with a small series of unanesthetized animals; other phases could use animals breathing spontaneously under light anesthesia. Judicious increases in duration of the incapacitation period and the energy and frequency of the pulses should yield useful approximations of the desired thresholds for humans. Other studies on the operation of electrodes and power supply could be conducted at the same time, Once burn thresholds have been established, the "no-let-go" threshold could be documented with a brief study using a palm-to-shoulder current path in human volunteers.

2. Encourage development of systems to fit specific needs. Any single electrical system is unlikely to prove optimum fon all situations in which incapacitation is desired, especially with regard to making two appropriate electrical contacts with the subject's body and maintaining them if prolonged incapacitation is required.

3. High voltage is likely to prove the most practical way to overcome the skin resistanze problem in many situations; if high voltage is used, the

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likclihood of small-area third degree skin burns must be accepted. High voltagc systems will need special provisions to avoid: (l) delivering excessivc current to the subject after a fall in skin resiatance; (2) shocking the operator; or (3) short circuits that could destroy effectivencss of the system before or after the start of incapacitation.

4. A short-range (arm's length) electrical current incapacitation device could be operational in a few months. The device cculd be a "pain dispenser" carried in the hand, and could consist of a modified surgical towel clip with battery-powered electronics to provide painful shocks.

5. Proposed systems should be examined critically, especially with regard to the resistance problem and the location of the entry and exit points for current flowing through the body. Unless a system has a reliable method of preventing current flow through the subject's chest, it should be assurned that current will flow through the chest in some cases. A single electrode with "ground" system is likely to be dependable in special situations only.

6. All systems intended to maintain incapacitation for more than a few seconds shou'd deliver currents well above the "no-let-go" threshold in order to insure that the subject will not be able to break contact manually.

7. Operators should be aware that a subject's gun is likely to be fired if the subject has a finger on the trigger at the moment electrical incapacitation starts.

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REFERENCES

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