Estimation of contributors

[Willi_...@gmx.de]

calculating LQ needs always the estimation of the number of contributors. My request about that is: What happens when you’re wrong?

 

E.g.: in our lab we had tested a family of two parents and four children touching varying items. The clou was that we knew in advance who had touched what.

We also generated mixtures from members of the family + one or two non relative persons.

In the end scientist tried to decipher the mixtures. And what to say? It didn’t come that easy for sure. Mostly mixtures looked like two person mixtures but where touched by more than two relatives.

 

So with this possibility of misinterpretation there is a risk two underestimate the number of contributors.

 

(On the other hand, when you falsely include stutters, or you even don’t know, the number can be higher than it has to be.)

 

So what is the result on the perspective of defense when you underestimate the number of related contributors in your calculation? Is that an issue?

(for overestimation it should be in the interest of defense I guess J)

 

What do think about?

Best

Christian

[hinda haned]

Hi Christian,

Thank for your question. 

The uncertainty about the number of contributors is part of the evaluation of forensic profiles, and there are multiple tools and methods you can use to factor that in your evaluation. 

I can recommend the following papers I contributed to (see enclosed) that can bring some elements of answer to your questions, but there are more that are also very useful and relevant.

I hope this helps.

Hinda

*-------------------*

The effect of varying the number of contributors on likelihood ratios for complex DNA mixtures

CCG Benschop, H Haned, L Jeurissen, PD Gill, T Sijen

Forensic Science International: Genetics 19, 92-99

Complex DNA mixture analysis in a forensic context: evaluating the probative value using a likelihood ratio model

H Haned, CCG Benschop, PD Gill, T Sijen

Forensic Science International: Genetics 16, 17-25

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Hinda