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DUI LIBRARY | Scientific Method


The Scientific Method


Scientific Method

To determine whether a scientific opinion, a forensic conclusion or test result can be relied upon we start with the scientific method. 

The scientific method is a process that attempts to answer a question. If a forensic opinion, conclusion or measurement was not the product of the scientific method – then it is not science. 

You start by identifying the question want to answer or a problem you want to solve.  Then you gather data which is used to form a hypothesis.  Then you test your hypothesis by trying to prove it wrong. All generally accepted scientific knowledge is the product of some form of this process.  


Truly scientific understanding cannot be attained or even pursued effectively when explanations not derived from or tested by the scientific method are accepted.

National Academy of Sciences and National Research Council (1984), pp. 8-11. Tweet

Do Courts Care About Scientific Method?

The scientific method is the rule.  If you don’t follow the rule, then you don’t have science.  You have something that just looks like science.  And probably is closer to propaganda.

As noted in Daubert, “in order to qualify as ‘scientific knowledge,’ an inference or assertion must be derived by the scientific method.” 

Logerquist v. McVey, 196 Ariz. 470, 496, ¶ 91, 1 P.3d 113, 139 (2000)(citing Daubert v. Merrell Dow Pharm., 509 U.S. at 590, 113 S.Ct. at 2795.)(Thus, scientific validity must precede evidentiary reliability.)

Courts are supposed to apply this scientific standard.  However, real-life examples of courts scrutinizing the government’s evidence using the scientific method are almost impossible to find.

But if Courts...

How can you use the scientific method?  By exploiting the ignorance of the adverse expert in front of the jury.  If a court doesn’t properly vet evidence for scientific validity before trial then you should be able to do so at trial. 

Cross-Examination Questions

The Scientific Method is Required

What is the scientific method?

There is at least a 50% chance they will struggle with the answer.  Sometimes they will answer gas chromatography.  To which you respond not “a” scientific method – but “the” scientific method. Do not be concerned that this is an open ended question.  The answer helps you whether it is correct or not.

All valid science is the product of the scientific method?

If the expert says no then ask: what generally accepted area of science is not the product of the scientific method? 

How did you utilize the scientific method when you test the blood in this case?

The answer is usually interesting.  More importantly, the jury will expect that the answer should not be as hard to give it will be before their eyes.

Your Word is Not Good Enough

In science, there must be objective standards to measure against?

Trust is not part of the scientific method?

Neither is faith?

Burden of Truth In Science

In science, burden of proof is on the proponent?

That is, the burden is on the person offer the opinion?

The conclusion?

As is the case here, the test result?

You Must Show Your Data

You have heard the phrase Ignorance is bliss?

Can we agree, in science, ignorance is not bliss?


Chapter 3

The science of measurement.

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