Blood Alcohol Levels
Police Crime Reference Number: 2524/10
Introduction:
On Sunday the 21st of November a suspected murder has taken place in
the form of death by dangerous driving.
It took place at 23.30 when the emergency services were called out to the
incident on the A520 from Meir to Stone.
On arriving at the road traffic collision it was seen that several cars had
been involved including a blue Subaru Impreza which had collided with the
raised rock embankment at the side of the road trapping and seriously injuring
the driver, now known to be Mr Steve SPEED and killing the single
passenger.
Two other cars were involved in the road traffic collision which received
damage and passengers received minor injuries. Statements taken from the
witnesses and victims indicated that the Subaru performed a dangerous
overtaking manoeuvre into oncoming traffic making this the cause of the road
traffic collision.
It took the fire service over an hour to extract SPEED out of the Subaru
and he was taken to Stafford A&E. Officers attending the hospital arrested
SPEED and with the agreement of the doctor a blood sample was taken and
retained as evidence ARD/22. The time elapsed since the incident was 3.75.
Forensic Strategy:
The items that were received for analysis were the blood sample of
Steve SPEED exhibit number ARD/22.
The points to prove in this investigation are:
1. Perform a quantitative analysis of the blood sample to determine the
amount of alcohol in the sample.
2. Determine whether or not the drivers blood-alcohol levels was above
the legal limit of 80mg/100ml at the time of the incident (taking into
account the metabolism and elimination of alcohol from the blood in the
time since the incident).
3. Report on the precision of your analysis and the validity of the
analytical method used.
All of the above are reflections of the advice, the case strategy and the
decisions that have been agreed between the investigator, prosecutor and
where appropriate the forensic scientist.
The analytical techniques that where chosen were gas chromatography.
Gas chromatography - specifically gas-liquid chromatography - involves a
sample being vaporised and injected onto the head of the chromatographic
column. The sample is transported through the column by the flow of inert,
gaseous mobile phase. The column itself contains a liquid stationary phase
which is adsorbed onto the surface of an inert solid. It’s very precise and will
distinctly show us how much alcohol is in SPEEDs’ blood.
This is a diagram of a gas chromatography machine:
Technical information:
Gas chromatography is used in analytic chemistry for separating and
analyzing compounds that can be vaporized without decomposition. Typical
uses of GC include testing the purity of a particular substance, or separating
the different components of a mixture (the relative amounts of such
components can also be determined). In some situations; GC may help in
identifying a compound.
In gas chromatography, the moving phase (or "mobile phase") is a
carrier gas, usually an inert gas such as helium or an unreactive gas such as
nitrogen. The stationary phase is a microscopic layer of liquid or polymer on
an inert solid support, inside a piece of glass or metal tubing called a column
(a homage to the fractionating column used in distillation). In our case we
used gas chromatography when it was in its stationary phase.
A gas chromatography machine we will begin the examination by filling
in the initial examination form which lists the date and start time of the
examination, the exhibit number and the evidence bag number, the
description on the evidence bag, description of packaging – including any
security features and continuity features. This is to make sure the description
on the evidence bag fairly summarises the piece of evidence inside the bag.
The blood sample ARD/22 will be put into the gas chromatography
machine 3 times to make it a fair test.
Results:
The results we gather are as follows:
*****ARD/22
Group 1:+ Test 1 : 135978
+ Test 2 : 140391
+ Test 3 : 140431
Group 2:+ Test 1 : 152499
+ Test 2 : 151069
+ Test 3 : 129593
Group 3:+ Test 1 : 143669
+ Test 2 : 146735
+ Test 3 : 114879
Group 4:+ Test 1 : 153543
+ Test 2 : 103512
+ Test 3 : 101605
*******40mg /100ml Calibration Standard (we made this ourselves in the lab
for comparison against ARD/22)
Group 1:+ Test 1 : 202872
+ Test 2 : 143495
+ Test 3 : 121712
Group 2:+ Test 1 : 144021
+ Test 2 : 205241
+ Test 3 : 251758
Group 3:+ Test 1 : Anomoly result
+ Test 2 : 266132
+ Test 3 : 162536
Group 4:+ Test 1 : 187881
+ Test 2 : 174966
+ Test 3 : 195196
Conclusion:
In conclusions I feel that the gas chromatography machine shows very
specific and accurate results meaning that you can always see what other
substance is in a solution. In our case the substance was alcohol in blood and
we could successfully see that SPEED did have alcohol in is blood at the time
of the crash.
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