In the past, we have blogged on the severe limitations on pattern recognition as a forensic science discipline. (Pattern Recognition is it Science or an Art?). In fact, the National Research Council of the National Academy of Sciences pointed to one form a pattern recognition as being most problematic: forensic odontology. Most broadly defined, it is […]
Standards, Controls, Calibrators, and Verifiers, Oh my…
Lions and Tigers and Bears… Verifiers, Calibrators and Controls… Oh my! Sometimes a criminal defense attorney can at times feel like Dorothy in the Wizard of Oz in that we are transported from the relative safety of home (the courtroom) to the weird world of Oz (the laboratory). There are unusual and often times conflicting […]
Why single column Gas Chromatography-Flame Ionization Detector analysis is not forensically or scientifically acceptable
There is a large difference between a single column analysis and a dual column analysis when it comes to the ability to most correctly identify and quantitate an unknown in the scientific world. In forensic science, we are constantly testing unknowns. What is meant by this is that we have a sample that is seized […]
Police Science: Re-purposing of Capilliary Columns for Drugs of Abuse testing
As I have written before a lot of forensic science is really legitimate analytical chemistry that is re-purposed for the courtroom, but without proper scientific method validation before deploying it into this new purpose. This re-purposing of legitimate techniques and employing them without examining the true validity of doing so is not scientific. I call […]
Co-elution in a nutshell
Co-elution is a very important concern in forensic chromatography. In a nutshell co-elution can be defined as when non-resolved (non-separated) compounds elute (come off) the column at the same time. It comes comes in two forms: (1) lack of specificity (inter-sample co-elution), and (2) analytical carry-over (intra-sample co-elution). Lack of specificity: A Gas chromatograph is […]
A Gas Chromatoagraph or Liquid Chromatograph is not like a calculator
I am fond of pointing out that a Gas Chromatograph (GC) and a Liquid Chromatograph (LC) are not like a simple calculator where anyone walking up to a calculator regardless if it is a 2 year old or a PhD in mathematics who keys in 2+2, the result will always be 4, it requires interpretation […]
Method Validation for Lawyers Part 6: What is quality assurance and quality control?
In a series of posts, we are going to talk about method validation. Part 1: Introduction-Is it valid, invalid or non-validated? Part 2: What is method validation? Part 3: Can we use someone else’s validated method? Part 4: What triggers verification, re-validation or out right new validation of a method? Part 5: What are the […]
Method Validation for Lawyers Part 5: What are the essential terms in method validation?
In a series of posts, we are going to talk about method validation. Part 1: Introduction-Is it valid, invalid or non-validated? Part 2: What is method validation? Part 3: Can we use someone else’s validated method? Part 4: What triggers verification, re-validation or out right new validation of a method? Part 5: What are the […]
Method Validation for Lawyers Part 4: What triggers verification, re-validation or out right new validation of a method?
In a series of posts, we are going to talk about method validation. Part 1: Introduction-Is it valid, invalid or non-validated? Part 2: What is method validation? Part 3: Can we use someone else’s validated method? Part 4: What triggers verification, re-validation or out right new validation of a method? Part 5: What are the […]
Method Validation for Lawyers Part 3: Can we use someone else’s validated method?
In a series of posts, we are going to talk about method validation. Part 1: Introduction-Is it valid, invalid or non-validated? Part 2: What is method validation? Part 3: Can we use someone else’s validated method? Part 4: What triggers verification, re-validation or out right new validation of a method? Part 5: What are the […]
Method Validation for Lawyers Part 2: What is method validation?
In a series of posts, we are going to talk about method validation. Part 1: Introduction-Is it valid, invalid or non-validated? Part 2: What is method validation? Part 3: Can we use someone else’s validated method? Part 4: What triggers verification, re-validation or out right new validation of a method? Part 5: What are the […]
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