Forensic Science - ACS Publications

12 Recovery and Identification of Residues of Flammable Liquids from Suspected Arson Debris C E C I L E. YATES, JR.

Downloaded by CORNELL UNIV on September 15, 2016 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0013.ch012

Chemical Science Research Unit, F.B.I. Laboratory, Washington, D. C. 20535

Estimates of the r a n g e of a n n u a l fire costs a s high a s $5 billion. These e s t i m a t e s include loss of use, fire suppression expenses and other factors (1). It is also estimated that as high as 40% of all fire damage is caused by arsonists. Therefore, the forensic chemist's examination in the laboratory and the subsequent court testimony to the identification of the flammable accelerant is extremely important to the success of the prosecution. Forensic chemists routinely receive debris associated with fires of incendiary origin and ordinarily attempt to establish whether or not a trace of a flammable liquid is present in the debris. The purpose of the forensic chemist's examination is that of establishing the "intent" of the arsonist, a requirement under most statutes (2). "Intent" eliminates suspicions of fires of natural and accidental origins. This paper presents a current summary of methods and instrumentation utilized in the recovery and analysis of traces of flammable accelerants in arson debris.

in t h e U. S. go physical damage,

Instrumentation A P e r k i n - E l m e r m o d e l 900 gas c h r o m a t o g r a p h w i t h a h y d r o g e n f l a m e i o n i z a t i o n d e t e c t o r i s u s e d i n t h i s w o r k . The r e c o r d e r i s a P e r k i n - E l m e r m o d e l 56 a d j u s t e d t o p r o d u c e a c h a r t a t 1 c e n t i m e t e r p e r m i n u t e f o r e a s e o f i n t e r p r e t a t i o n and e v a l u a t i o n . V a r i a t i o n s i n a t t e n u a t i o n are f r e q u e n t l y necessary from specimen t o specimen. The c o l u m n w h i c h g i v e s t h e most e f f e c t i v e s e p a r a t i o n o f t h e mixtures o f accelerants g e n e r a l l y encountered i s a SupportC o a t e d , Open T u b u l a r (SCOT) c o l u m n c o m m e r c i a l l y a v a i l a b l e f r o m Perkin-Elmer Corporation. The s t a i n l e s s s t e e l c o l u m n i s 0.020 i n c h i n n e r d i a m e t e r c o a t e d w i t h DC 550 o n a n i n e r t s u p p o r t and c o n s i s t s o f two f i f t y - f o o t s e c t i o n s j o i n e d w i t h a z e r o d e a d

108

Davies; Forensic Science ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

12.

YATES

Residues

of Flammable

Liquids

109

volume u n i o n . The c a r r i e r u t i l i z e d i n a n a l y z i n g a c c e l e r a n t s i s h e l i u m , s e t t o produce a f l o w r a t e o f approximately 5 m i l l i l i t e r s per minute.


Procedure: Samples a r e i n t r o d u c e d t o t h e i n s t r u m e n t w i t h s y r i n g e s o f various types and s i z e s through a c a p i l l a r y i n j e c t i o n system w i t h a m a n i f o l d t e m p e r a t u r e o f 200°C. T h e t y p e o f s y r i n g e u s e d depends u p o n t h e s a m p l e t o b e a n a l y z e d : headspace sample i n j e c t i o n s a r e made w i t h 2 m l d i s p o s a b l e p l a s t i c s y r i n g e s , a n d l i q u i d samples a r e i n j e c t e d w i t h l u i m i c r o s y r i n g e s , u s u a l l y u s i n g O . l u l i f the l i q u i d i s f a i r l y pure. A programmed r u n h a s b e e n f o u n d t o b e h i g h l y e f f e c t i v e i n a n a l y z i n g a c c e l e r a n t s and i s p r e f e r r e d over i s o t h e r m a l runs. The p r o g r a m d e t e r m i n e d t o b e b e s t f o r m o s t a c c e l e r a n t s a m p l e s i s : I n i t i a l t e m p e r a t u r e ( I . T . ) - 70°C I.T. h e l d f o r 3 m i n u t e s a t 70°C T e m p e r a t u r e I n c r e a s e - 6°C p e r m i n u t e Maximum T e m p e r a t u r e - 145° C T o t a l Maximum Time - 45 m i n u t e s I t i s n o t i n f r e q u e n t t o o b t a i n i n t h i s manner a c h a r t w i t h a s many a s 150 o r more d i s t i n c t p e a k s . Methods o f Recovery Numerous methods a r e a v a i l a b l e i n t h e r e c o v e r y o f t r a c e q u a n t i t i e s o f flammable a c c e l e r a n t s f r o m a r s o n d e b r i s . Of t h e s e , f o u r b a s i c methods a r e g e n e r a l l y p r e f e r r e d a n d h a v e b e e n f o u n d t o b e a d e q u a t e i n most c a s e s e n c o u n t e r e d b y f o r e n s i c chemists. E a c h o f t h e s e methods p o s s e s s e s g o o d a n d b a d f e a t u r e s and c o n s i d e r a t i o n must b e g i v e n t o t h o s e f e a t u r e s i n contemplating the recovery o f a c c e l e r a n t s from any p a r t i c u l a r piece o f evidence. L i q u i d . T h e m o s t p r e f e r a b l e o f t h e methods a v a i l a b l e i s t h e u s e o f a l i q u i d s u c h a s t h a t f o u n d i n a n unconsumed, u n b r o k e n molotov c o c k t a i l o r i n a g a s o l i n e can c o n t a i n i n g the remains o f t h e flammable l i q u i d used i n the i n i t i a t i o n o f a f i r e . This t y p e o f sample i s t r a n s f e r r e d t o a n a i r t i g h t c o n t a i n e r and subsequently s u b j e c t e d t o examination w i t h the gas ehromatograph. Pure l i q u i d i s the best source o f m a t e r i a l f o r the i d e n t i f i c a t i o n o f flammable l i q u i d s and i n the comparison o f q u e s t i o n e d m a t e r i a l w i t h known s t a n d a r d s . A very small quantity o f m a t e r i a l i s needed (0.]yal) a n d v e r y l i t t l e t i m e i s u t i l i z e d s i n c e instrument programs can be p r e - s e t , thereby e l i m i n a t i n g the n e c e s s i t y f o r r e p e a t i n g runs w i t h adjustments t o the instrument. Should t h e presumably pure l i q u i d c o n t a i n an unsuspected c o n t a m i n a n t , i t c o u l d c a u s e damage t o t h e i n s t r u m e n t . Materials


110

FORENSIC

SCIENCE


f r e q u e n t l y encountered as contaminants i n whole l i q u i d a r e p l a s t i c i z e r s , adhesives, and o t h e r m a t e r i a l s solui;le i n accelerant mixtures. These substances c a n contaminate t h e d e t e c t o r and r e d u c e o r d e s t r o y t h e e f f i c i e n c y o f t h e column. Steam D i s t i l l a t i o n . Many t y p e s o f m a t e r i a l s r e c e i v e d c a n be p r e p a r e d f o r a n a l y s i s b y means o f s t e a m d i s t i l l a t i o n . These items f r e q u e n t l y possess r e a d i l y detectable odors i n d i c a t i n g t h a t an adequate q u a n t i t y o f m a t e r i a l i s a v a i l a b l e i n t h e specimens f o r recovery by d i s t i l l a t i o n . These i t e m s i n c l u d e fragments o f wood, s o i l , d r a p e r y a n d c a r p e t i n g . I t e m s t o b e e x a m i n e d must n e c e s s a r i l y be s u i t a b l e f o r " p a r t i a l d e s t r u c t i o n , " s i n c e f i n g e r p r i n t s a r e l o s t , s h r i n k a g e f r e q u e n t l y o c c u r s , and o t h e r changes r e l a t e d t o immersion i n h o t w a t e r a r e seen. G e n e r a l l y , when t h e o d o r o f a n a c c e l e r a n t i s s t r o n g , t h e success o f recovery i s assured. I n a d d i t i o n , t h i s method i s i d e a l i n t h e recovery o f q u a n t i t i e s o f accelerant from substances such as p l a s t i c s , r u b b e r goods, r e s i n o u s m a t e r i a l s and o t h e r s which e i t h e r absorb o r d i s s o l v e i n flammable a c c e l e r a n t s . However, t h i s p r o c e d u r e i s l i m i t e d i n r e c o v e r i n g a c c e l e r a n t s from m i x t u r e s o f foaming agents such as soaps. These i t e m s a r e f r e q u e n t l y encountered by t h e f o r e n s i c chemist i n sabotage cases and i n c e n d i a r y d e v i c e s . A l t h o u g h l i m i t e d t o a t e m p e r a t u r e maximum o f 100°C, a g o o d r e p r e s e n t a t i o n o f t h e more v o l a t i l e f r a c t i o n s c a n b e r e c o v e r e d by s t e a m d i s t i l l a t i o n w i t h a r e f r i g e r a t e d c o n d e n s e r . W h i l e v e r y s i m p l e a n d e v e n c l u m s y i n some a s p e c t s , t h i s method i s e x t r e m e l y e f f e c t i v e w i t h many t y p e s o f e v i d e n c e . S o l v e n t Wash. Hardwood, p o r c e l a i n , g l a s s , m e t a l a n d s i m i l a r h a r d - s u r f a c e d i t e m s l e n d t h e m s e l v e s t o t h e s o l v e n t wash t e c h n i q u e of recovery. U s u a l l y , no odors c a n be d e t e c t e d and i n d i c a t i o n s are that a very small quantity o f only the h i g h - b o i l i n g f r a c t i o n s o f a n a c c e l e r a n t remain f o r r e c o v e r y . A f t e r p l a c i n g t h e specimen i n a s u i t a b l e c o n t a i n e r f o r washing, t h e i t e m i s g i v e n s e v e r a l washings o f a s o l v e n t such as hexane. V i r t u a l l y a l l o f t h e f r a c t i o n s o f an a c c e l e r a n t p r e s e n t c a n b e r e c o v e r e d f r o m a r s o n d e b r i s i n t h i s manner, a n d t h e q u a n t i t y can be concentrated by a c a r e f u l e v a p o r a t i o n o f t h e s o l v e n t t o a s m a l l q u a n t i t y . U n f o r t u n a t e l y , many c o n t a m i n a n t s a r e r e c o v e r e d a l o n g w i t h t h e a c c e l e r a n t t r a c e s . V i r t u a l l y any c l e a n i n g " o f t h e s o l v e n t wash w i l l n e c e s s a r i l y e l i m i n a t e v a l u a b l e q u a n t i t i e s o f t h e a c c e l e r a n t . Among t h e c o n t a m i n a n t s e n c o u n t e r e d by t h i s r e c o v e r y method a r e o i l s , a d h e s i v e s , r e s i n s a n d plasticizers. T h e s e a r e f r e q u e n t l y u n o b s e r v e d a n d may c a u s e damage t o t h e i n s t r u m e n t . Headspace. R e c o v e r i n g vapors f r o m t h e atmosphere above a specimen i n a s e a l e d , heated c o n t a i n e r i s o f t e n a s a t i s f a c t o r y method o f a n a l y z i n g s p e c i m e n s w h i c h c a n n o t b e t r e a t e d b y t h e



12.

YATES

Residues

of

Flammable

Liquids

111

o t h e r methods d e s c r i b e d . Such specimens i n c l u d e i t e m s o f c l o t h i n g t h a t cannot be a l t e r e d o r d e s t r o y e d , l e a t h e r goods, canvas, items o f f a b r i c , specimens contaminated w i t h foaming agents such as soap, and absorbent p l a s t i c s and rubber. A group o f i t e m s , such a s p i e c e s o f c l o t h i n g o r s e v e r a l documents, c a n be h a n d l e d a t one t i m e and w i t h o u t d e s t r o y i n g f i n g e r p r i n t s , w r i t i n g or other aspects o f f o r e n s i c i n t e r e s t . A l t h o u g h t h i s method i s t h e o n l y o n e a p p l i c a b l e i n many i n s t a n c e s , s e v e r a l problems present themselves. Valuable time i s spent i n attempting t o f u r t h e r vaporize remaining t r a c e s o f accelerants. A d d i t i o n a l l y , since low b o i l i n g f r a c t i o n sare u s u a l l y already l o s t and t h e h i g h b o i l i n g f r a c t i o n s a r e d i f f i c u l t t o v a p o r i z e , problems a r e f r e q u e n t l y encountered i n e v a l u a t i n g t h e chromatograms o b t a i n e d . Great v a r i a t i o n s a r e found t o e x i s t f r o m s a m p l e t o s a m p l e due t o t h e a b s o r b a n c y o f t h e m a t e r i a l s b e i n g examined and t h e environment e x i s t i n g where t h e specimen was c o l l e c t e d a n d s e a l e d . O t h e r M e t h o d s . O t h e r methods o f r e c o v e r y o f t r a c e s o f f l a m m a b l e l i q u i d s u s e d i n f r e q u e n t l y a r e vacuum d i s t i l l a t i o n a n d s o a k i n g i n w a t e r . Most i t e m s o f a r s o n e v i d e n c e a r e p h y s i c a l l y more s u s c e p t i b l e t o a n a l y s i s b y o t h e r methods t h a n b y vacuum distillation. S o a k i n g i n w a t e r w i l l sometimes a l l o w r e s i d u e s f r o m s m a l l p i e c e s o f wood t o s u r f a c e ; t h e y c a n t h e n b e c o l l e c t e d and a n a l y z e d . T h e s e methods a r e u s u a l l y h i g h l y i n e f f i c i e n t a n d l i t t l e s u c c e s s i s e x p e r i e n c e d w i t h them. Comparison The c h a r t s p r o d u c e d b y t h e g a s c h r o m a t o g r a p h q u i c k l y i n d i c a t e t h e success o r f a i l u r e o f t h e techniques selected i n a t t e m p t i n g t o r e c o v e r t r a c e s o f a c c e l e r a n t . When compared w i t h c h a r t s o f known s t a n d a r d a c c e l e r a n t s p e c i m e n s , t h e r e s u l t s r a n g e from s i m p l e comparisons t o c h a r t s e x t r e m e l y d i f f i c u l t t o match. F r e q u e n t l y , p u r e l i q u i d samples produce c h a r t s t h a t a r e e s s e n t i a l l y a p e r f e c t match f o r each peak, b o t h by r e t e n t i o n and q u a n t i t y . T h i s a l l o w s a q u i c k and c e r t a i n i d e n t i f i c a t i o n . However, a s i n d i v i d u a l s a m p l e s o f a c c e l e r a n t s a r e " w e a t h e r e d " b y e x p o s u r e t o f i r e a n d a i r t h e more v o l a t i l e , l o w - b o i l i n g f r a c t i o n s a r e consumed o r l o s t t h r o u g h e v a p o r a t i o n . The c o m p o s i t i o n s o f some a c c e l e r a n t m i x t u r e s s u c h a s g a s o l i n e a r e r a p i d l y a l t e r e d . W i t h p a s s a g e o f t i m e , " w e a t h e r e d " a c c e l e r a n t m i x t u r e s become more d i f f i c u l t t o compare w i t h c h a r t s o f s t a n d a r d m i x t u r e s . I n a d d i t i o n , t h e m i x i n g o f t w o o r more a c c e l e r a n t s may p r o d u c e a s a m p l e t h a t i s v i r t u a l l y i m p o s s i b l e t o i d e n t i f y . The chromatogram p r o d u c e d f r o m such a sample i s d i f f i c u l t t o a s s o c i a t e w i t h a s i n g l e o r i g i n a l a c c e l e r a n t o r w i t h a known mixture o f a c c e l e r a n t s prepared by t h e f o r e n s i c chemist s i n c e he i s e s t i m a t i n g t h e r a t i o s o f a c c e l e r a n t m i x t u r e s h e s u s p e c t s t o be p r e s e n t i n t h e q u e s t i o n e d sample.


112

FORENSIC SCIENCE

Frequently, the r e s i d u a l p o r t i o n of the accelerant present i n a r s o n d e b r i s may be s o s m a l l i n q u a n t i t y t h a t t h e c o m p a r i s o n o f t h e r e s u l t i n g chromâtogram w i t h a known s t a n d a r d i s inconclusive.


Recovery Problems Numerous p r o b l e m s a r e e n c o u n t e r e d i n t h e r e c o v e r y o f a c c e l e r a n t m a t e r i a l s f r o m submitted specimens. These problems l i m i t t h e p o t e n t i a l i d e n t i f i c a t i o n o f a c c e l e r a n t s and a r e o f t e n p r e c i p i t a t e d by t h e l a c k o f c a r e t a k e n b y t h e i n v e s t i g a t o r i n c o l l e c t i n g and h a n d l i n g t h e s p e c i m e n s . Many s p e c i m e n s o b t a i n e d by t h e i n v e s t i g a t o r a r e s i m p l y n o t appropriate. Rather than submitting a piece of drapery or carpeting, which are h i g h l y absorbent, pieces o f g l a s s , ceramics o r s i m i l a r s m a l l , hard-surfaced, non-absorbent m a t e r i a l s are taken. L i m i t e d s u c c e s s i s e x p e r i e n c e d w i t h t h e non-abs o r b e n t materials. F u t h e r m o r e , d i f f i c u l t y i s e n c o u n t e r e d w i t h many s p e c i m e n s r e c e i v e d f o r examination e i t h e r because o f the absence o f a c c e l e r a n t o r because o f the type o f m a t e r i a l i t s e l f . Examples a r e ( a ) h e a v i l y c h a r r e d wood, w h e r e a l l f l a m m a b l e a c c e l e r a n t h a s b e e n l o s t , ( b ) a r a g t h a t was s o a k e d i n t h e w a t e r u s e d by t h e f i r e d e p a r t m e n t t o e x t i n g u i s h t h e b l a z e , d r i e d o u t , and f o r w a r d e d t o t h e f o r e n s i c c h e m i s t f o r e x a m i n a t i o n and ( c ) a s a m p l e o f s o a p r e c o v e r e d n e a r t h e s i t e o r o r i g i n . A n a l y s i s o f t h e soap f o r an a c c e l e r a n t w o u l d e x c l u d e t h e s o l v e n t wash r e c o v e r y method a s w e l l as any o t h e r method t h a t m i g h t c a u s e i n t e r f e r e n c e due t o foaming. Improper

Handling

I f a s a m p l e i s p r e p a r e d c o r r e c t l y , no v a p o r s o f a c c e l e r a n t s w i l l be l o s t o n c e i t i s p l a c e d i n a n a d e q u a t e c o n t a i n e r a n d p r o p e r l y s e a l e d ( J ) . Many good s p e c i m e n s a r e h a n d l e d s u b s e q u e n t t o r e c o v e r y i n s u c h a way t h a t t h e f l a m m a b l e a c c e l e r a n t s p r e s e n t are l o s t . Upon r e a c h i n g t h e f o r e n s i c c h e m i s t , he e i t h e r h a s v e r y l i t t l e a c c e l e r a n t t o r e c o v e r and e x a m i n e , o r h e h a s n o n e . Porous c o n t a i n e r s and wrappers s u c h as p a p e r bags, b u n d l e s o f newspapers and c a r d b o a r d boxes a r e f r e q u e n t l y s u b s t i t u t e d f o r suitable a i r t i g h t containers. In these instances, v o l a t i l e materials are i n v a r i a b l y l o s t through evaporation. The q u a n t i t y o f d e b r i s r e c e i v e d i s f r e q u e n t l y a g r e a t o b s t a c l e t o t h e s u c c e s s f u l r e c o v e r y o f a n i d e n t i f i a b l e amount o f flammable l i q u i d . S m a l l amounts o f d r y , c h a r r e d a s h e s , d r y fragments o f p a p e r , and s m a l l fragments o f g l a s s c o u l d a t t h e very best only contain extremely small q u a n t i t i e s of accelerants and c o u l d e a s i l y p r e c l u d e t h e p o s s i b i l i t y o f e f f e c t i n g a n i d e n t i f i c a t i o n of the m a t e r i a l .


12.

YATES

Residues

of

Flammable

Liquids

113


Conclusion T h r o u g h t h e u s e o f t h e v a r i o u s methods o f r e c o v e r y discussed, i t i s o f t e n p o s s i b l e f o r the f o r e n s i c chemist t o o b t a i n a s a t i s f a c t o r y sample o f a c c e l e r a n t r e s i d u e f o r e x a m i n a t i o n p u r p o s e s . T h r o u g h u t i l i z a t i o n o f gas c h r o m a t o g r a p h y , t h e i d e n t i f i c a t i o n o f t h e a c c e l e r a n t c a n o f t e n be e f f e c t e d and d i f f e r e n c e s a n d s i m i l a r i t i e s b e t w e e n r e c o v e r e d and known s t a n d a r d s p e c i m e n s c a n be shown. However, s u c c e s s i n t h e r e c o v e r y and i d e n t i f i c a t i o n o f a c c e l e r a n t r e s i d u e s i s h i g h l y d e p e n d e n t u p o n t h e t y p e and q u a n t i t y o f m a t e r i a l r e c e i v e d f o r e x a m i n a t i o n and t h e c a r e t h a t has been t a k e n i n t h e p r e s e r v a t i o n o f t h e i t e m s t o be e x a m i n e d . Obvious areas o f p o t e n t i a l r e s e a r c h present themselves t o the f o r e n s i c chemist. 1. A n e e d f o r a d d i t i o n a l and b e t t e r methods o f r e c o v e r y o f t r a c e s o f a c c e l e r a n t s . T h e s e methods must be i n e x p e n s i v e , p r a c t i c a l and s i m p l e i n o r d e r f o r l e s s e r - e q u i p p e d f o r e n s i c l a b o r a t o r i e s t o u t i l i z e t h e m t o t h e maximum. 2. A n e e d f o r s i m p l e , i n e x p e n s i v e methods o f r e m o v i n g contaminants from recovered t r a c e s o f a c c e l e r a n t s i n order t o a l l o w a s p e c i f i c i d e n t i f i c a t i o n t o be made o f t h e a c c e l e r a n t w i t h o u t damage t o t h e gas c h r o m a t o g r a p h . 3. A n e e d f o r methods o f s p e c i f i c a l l y i d e n t i f y i n g two o r more a c c e l e r a n t s when f o u n d t o g e t h e r i n a r e c o v e r e d s p e c i m e n . 4. A n e e d f o r t e c h n i q u e s t o i n d i v i d u a l i z e a c c e l e r a n t s by commercial brands o r sources a f t e r recovery from f i r e d e b r i s . Literature Cited 1.

"A S t u d y of Fire P r o b l e m s , " NAC-NRC 1961. 2. O'Hara, C. Ε., "Fundamentals of Criminal Investigation", Charles C. Thomas, Springfield, Ill., 1973, pp. 219 - 230. 3. Hurteau, W. Κ., "Arson Investigation and The Collecting of Evidence," Security World, March, 1974, p. 18.

publication

949, W.D.C.,


Forensic Science - ACS Publications

Recommend Documents