Debate and discussion of any biological questions not pertaining to a particular topic.
I don't know, but you may find some answers or interesting leads at least in this paper from the last issue of Science.
From what I understand, the answer is that your lab result should be delivered with a confidence interval that would tell you how much you can trust the results.
For individual, to have more than one DNA profiles is possible. That's what we called as chimera. It is because in their body has more than one different population of cells, which are genetically distinct, which originated in different zygotes. This multiple DNA profiles happens for instance after placing adoptive immunity and general transplantation or grafting.
alf: Hey, it seems a nice job of you. Forensic activities always interesting me much. We could discuss things if you have spare time. Just e-mail or PM me. I really want to learn this field. Thanks in advance.
I quote from the cited paper the interesting bit, and its reference:
Sorry, for linking to papers you cannot access, I have the bad habit to connect from the lab, where we have plenty of e-subscritions, and i sometimes forget that some place else these subscriptions do not exist...
Anyway, I hope this could be of some help
First and foremost, I extend my deepest appreciation, and gratitude to everyone that has responded to my inquiries regarding DNA profiles. I thank you for your time, attention, and obvious in-depth knowledge on this matter. It appears I have come to the right place, to assist me in my research on this subject.
If I may, let me give you a brief synopsis of this particular case. It may give you a clearer picture, of where I am heading with my many questions to follow.
In 1999, two persons was found shot to death, in a home, which is in my jurisdiction. Both victims were females. One of the females had been sexually assaulted. During evidence recovery, a sample of semen was recovered from the raped female. Initial DNA analysis revealed, that this specimen of semen, was not of the victims DNA profile. This semen sample is regarded as [foreign], therefore, considered to be the suspects semen. The investigation led us to Texas. In Texas, investigators interviewed a person. This person confessed to doing these crimes. He gave a very detailed confession. He revealed specific details, in which only the person that had committed this crime would know. He voluntarily submitted a sample of his blood, for DNA analysis. The result of the DNA comparisons, of the collected semen, and the suspects blood, revealed that they did not match.
Although we have not completely ruled out the possibility of there being two suspects, other evidence at the crime scene indicated that there was only one intruder.
Also, there was another violent crime which occurred not far from the double homicide. This crime occurred after the double homicide. It is believed that this crime was committed by the same person. The victim of this second crime survived the attacks. However, due to circumstances, she was not able to give a positive identification of the suspect.
I have many more questions for this forum. However, I must go for now, and get back to work. Again, thank you. I look forward to continuing this dialog with each and every one of you. Your knowledge, inputs, and references are alway welcome.
My research, thus far, has also revealed that, there has not been such a case as this, encountered and/or presented to law enforcement investigators, and/or the judicial system. This could be something - that we refer to in law enforcement as - "a landmark discovery". We all may be on to something here.
Thanks Again. I will be communicating with you all again soon.
Wow, you seem to have a real problem here. According to: http://gslc.genetics.utah.edu/features/forensics/
your case seems kind of fragile.
From what you give us:
first, semen sample would seem logically foreign to me if found in female body, don't you think?
More seriously, but I am no specialist in forensic science the semen could have been coming from another person having an intercourse with the victim before the murder (husband, boyfriend?). The rapist not leaving any semen (condom, failed attempt...).
I cannot suggest anything more, maybe the lab that did the DNA typing could discuss the method with you and suggest where the problem can be. At leasst they should know how they made the identification, which we don't know on this forum.
Well I guess you would ask that before sampling, but:
- How much blood would you transfer, probably much less than the 5L so at least the normal DNA would be making the majority in the mix.
- IIRC nowadays you give only useful blood parts needed (white cells, red cells, plasma, platelets,...) If he had red cells only, it would then be non significant.
Thank you for your input, and thank you for the web site, and literature references. I do appreciate your interest. You, along with the others, have been most helpful, and extremely informative.
A good investigator will always employ logic in all of his approaches, when considering every minute detail he/she will encounter while processing a crime scene, and when conducting an investigation. However, logic will not, nor will it ever be able to withstand the extreme scrutiny, an investigator will face in the courts of law. Nor can I ever just assume anything, when making important decisions at a crime scene, or during the investigation. If a good defense lawyer asked me a question, and, the words "I assumed" ever enter into my testimony, my credibility with the jurors just went out of the window.
My question to you is - Why would you automatically deem it logical, for any semen to be found in a female, to be foreign?
What you may not realize is, when I am investigating a crime, I am not only examining, analyzing, gathering facts, seeking/finding evidence, properly collecting that evidence, taking notes, conducting interviews, photographing the [entire] crime scene, as well as, supervising other officers that are on the scene, I am also preparing my case to be presented in court. I begin structuring my testimony, and court room presentation, immediately upon receiving the initial call to respond to a crime scene. I have to be ready, and able, to answer every possible question that is asked of me, by the Prosecutor, and defense lawyer(s).
In the world of facts, and legalities, one will find in a court of law, it is absolutely imparative, that an investigator, either confirm, or eliminate ["rule out"] all possibilities. In regards to this particular case, it was imparative, that it be absolutely determined that, the semen found in this victim, was not hers, and that, it was from someone else. We can never leave any stone unturned.
Remember: The burden of proof rests solely on the shoulders of the prosecution. If this case ever reaches a trial, we must be prepared to prove our case beyond a reasonable doubt. No stone can be left unturned.
We have also examined, and considered all of the other possibilites, that you have mentioned in your last responses. Due to the direction, and circumstances of this case, I have had to begin researching this particular facet of DNA. Which is what has brought me here.
I am fascinated by your inputs, and knowledge. Please keep them coming.
I am compiling a list of questions regarding this subject matter. Again, I look forward to continuing this dialogue with all of you in this forum.
Afaik, the lifespan of semen in female reproductive tracts is very limited due to the low pH and lacking of fructose. They will die and cleared by phagocytes.
As I said that to have a multiple DNA profiles of a single individual is possible, but to have a multiple DNA profiles in semen is out of my mind. It means that there must be at least two germ cells and it sounds impossible.
According to the description, in my innocence mind, I got some points here: It seems strange that he easily confessed and did not mind to be examined and accused as a suspect (sorry for my words, I do not know the proper terms). The sample semen from victims does not match with the one from the suspect. Is there any possibilites that the suspect is not a common one, means a psyco or someone with strange behavior? Or maybe there is a possibilities that someone else come to the scene after the murder and took advantage of the victims before the police came?
Oh I sound like trying to be Holmes I do not know anything about forensics and criminalities, so this seems very interesting to me, I feel like reading a famous story book before I realized this is a real fact. This is the first time I 'present' in the criminal scene
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