DNA test will clear my son: Koh Tao headman

[changnaam]

What is a 70% DNA match? I thought Chimpanzees DNA was more than 70% of a match.

Something to do with Gene Sequencing with regards to chimps, pigs and other life, I expect.

With 70% certainty they might as well say that it's a mammal that did it.

I do not pretend to know anything about DNA testing or matching, just quoting what RTP stated early in this case. They seemed to make it sound pretty significant.

[StealthEnergiser]

It would be worth the investigators finding out when and where he had his haircut.

[partington]

What is a 70% DNA match? I thought Chimpanzees DNA was more than 70% of a match.

Something to do with Gene Sequencing with regards to chimps, pigs and other life, I expect.

With 70% certainty they might as well say that it's a mammal that did it.

I do not pretend to know anything about DNA testing or matching, just quoting what RTP stated early in this case. They seemed to make it sound pretty significant.

Bear in mind that the vast majority of the RTP, and the the vast majority of newspapers reporting what they say have no understanding at all of what a DNA test measures, how the results are expressed and what the results mean. It's therefore a waste of time to get hung up on some form of words that was incorrect in the first place. In reality matches in DNA profiling are not ever expressed as a percentage.

If the suspect's DNA matches the DNA found at a crime scene, the result is expressed as a probability that the DNA at the crime scene could match the DNA of the suspect by chance, rather than it coming from him for certain.

What is measured are DNA markers at 10 (the UK method) or 13 (the US method) different places: each place has two numerical values. If the DNA sample is good, and the values at all 13 places can be measured, then a match has probabilities in the order of 1 to a trillion that the match happened by chance .

However if the DNA sample is degraded, or a mixture of a number of people, that can make a complete profile (two numerical values for each of the thirteen places) difficult or impossible to get. You might be able to get values for, say 8 of the 13 places . However you can still work out a probability that the match could have happened by chance, rather than because the suspect left the DNA at the crime scene. The fewer the places that you can get values for, the more likely it is that the match could happen by chance.

If you could get numerical values for example for only ONE of the 13 places, then the probability that a random person rather than the suspect left the DNA at the crime scene might be quite high, say 1 in 100. This would not be very good or convincing evidence.

In any case the DNA profile report would always give a probability, based on how clear the DNA evidence is, what the probability of matching this DNA profile by chance would be. It is not a percentage!

Edited November 8, 2014 by partington

[RickBradford]

What is a 70% DNA match? I thought Chimpanzees DNA was more than 70% of a match.

Something to do with Gene Sequencing with regards to chimps, pigs and other life, I expect.

With 70% certainty they might as well say that it's a mammal that did it.

Nah -- even the zebra fish shares 85% of DNA with humans.

Down at 70%, you're with the sea sponges.

[Scott]

We have two topics on the DNA from the village headman's son, so I will close this one.

Let's post in this topic:

http://www.thaivisa.com/forum/topic/773084-dna-results-from-ko-tao-village-heads-son-dont-match-traces-on-slain-british-tourists/

Thanks.

//CLOSED//