Mixture with a minor and a major contributor

[cecili...@gmail.com]

Hi Hinda, we have been using LRmix Studio for two years and it’s an excellent software!! I would like to ask you some questions:

 

1)                  One is very simple: when you add a profile manually the software have the Loci in a define order, it’s possible to change this order?

 

2)                  The other question I have is conceptual. In a case with a mixed crime-stain, the electropherogram have a minor contributor and a major contributor. The minor contributor shares many alleles with the suspect, but there are some missing alleles and we believe that drop-out occurs. The major contributor is an unknown person (it is not between the references profiles). Under the Hp (prosecutor hypothesis) we propose that the suspect (with drop-out > 0) and one unknown person (without drop-out or drop-out=0) contributed to the stain, and under the Hd (defence hypothesis) we propose that two (2) unknowns persons (with drop-out > 0) contributed to the stain. In Hd we propose drop-out >0 for both unknown persons: we know that the minor contributor is a “low template profile”, we believe that the other unknown person is not suffering drop-out,  but in the Hd you can’t distinguish the unknowns persons, isn’t it?.

Is this approach correct?, I wonder if it’s correct to consider the unknown person in the Hp proposition without drop-out and then both unknowns persons with drop-out in the Hd proposition.

Best regards and thanks Hinda!!!

[hinda haned]

Hi Cecilia my answers are enclosed

2017-03-07 19:33 GMT+01:00 <cecili...@gmail.com>:

Hi Hinda, we have been using LRmix Studio for two years and it’s an excellent software!! I would like to ask you some questions:

 

1)                  One is very simple: when you add a profile manually the software have the Loci in a define order, it’s possible to change this order?

No you cannot change it manually, but the order does not affect the numbers computed by the software. 

 

2)                  The other question I have is conceptual. In a case with a mixed crime-stain, the electropherogram have a minor contributor and a major contributor. The minor contributor shares many alleles with the suspect, but there are some missing alleles and we believe that drop-out occurs. The major contributor is an unknown person (it is not between the references profiles). Under the Hp (prosecutor hypothesis) we propose that the suspect (with drop-out > 0) and one unknown person (without drop-out or drop-out=0) contributed to the stain, and under the Hd (defence hypothesis) we propose that two (2) unknowns persons (with drop-out > 0) contributed to the stain. In Hd we propose drop-out >0 for both unknown persons: we know that the minor contributor is a “low template profile”, we believe that the other unknown person is not suffering drop-out,  but in the Hd you can’t distinguish the unknowns persons, isn’t it?.

Is this approach correct?, I wonder if it’s correct to consider the unknown person in the Hp proposition without drop-out and then both unknowns persons with drop-out in the Hd proposition.

Best regards and thanks Hinda!!!

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indeed, it is not possible to distinguish that unknown individuals have different dropout rates, by definition these are not known profiles, so relying on allele data alone, the software cannot distinguish them, 

LRmix Studio will  go through all combinations, assigning different dropout rates without distinguishing between combinations because we are not modeling peak height information, one thing you can do is explore the LR obtained with different dropout rates in the sensitivity analysis. Alternatively you can  extract the major donor profile and anchor it as a known major donor, with dropout zero, then you can simply vary the dropout for the other unknowns. I would suggest to explore both solutions. 

Best,

H.

 

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Hinda

[cecili...@gmail.com]

Thank you Hinda for your answer!!! I'll try your suggestions.
In any case, I wonder if it’s correct to consider the unknown person in the Hp proposition without drop-out and then both unknowns persons with drop-out in the Hd proposition. what do you thik about this?

To post to this group, send email to lrmix-studi...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/lrmix-studio-user-group/c25f641d-32b0-429b-b798-b9cde1d7a707%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

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Hinda