Module Eight

Question 1

Molecular biology

Answer 1

Nucleus are made up of chromosomes

Dna is a molecule made up of nucleotides that link together in a double helix

Question 2

What is DNS used for in Cjs

Answer 2

New investigative leads more openly w more evidence that is testable
Essentially leads to more arrests - isn’t circumstantial evidence anymore can sit on its own
More prosecutions possibly - can provide strong evidence
Power to exonerate wrongfully convicted

Question 3

What are the barriers to DNa

Answer 3

DNA databases what is collected and located and managed
DNA backlogs - usa 2002 260k back logged cases, 500k back logged requests for evidence testing not in system not being processed problem is getting worse

Question 4

Why are there backlogs

Answer 4

No identified suspect 
Suspect not charged
Guilty plea anticipated no need for evidence
Lack of funding
No request by prosecution

Question 5

Most cells contain nucleus made up of chromosomes (long strands of dna )

Answer 5

Dna is a complex molecule made up of nucleotides (bases) that link together in a double helix

Question 6

How does inheritance of genetic material work

Answer 6

Mum has for example A,B for her genetic information. Father has C,D. So children would be AC, AD, BC or BD. One gene from each parent.

Question 7

How do you extract dna

Answer 7

Extract dna from where found and from victim and offender. Cut stain of dna out put it into tiny pieces heat it w chemicals and breaks down weaker cells this skin cells left with pure DNA in suspended in a liquid like sperm cells stronger cells

Question 8

What are short tandem repeat testing

Answer 8

Current standard since late 1990s. Concerned w the number of times a sequence (at,cg) repeats itself at a given location on the chromosome location called locus at cg is the repeat this sequence. DNA testing looks at the lengths of those repeats. Estimate of a chance of a random match 13 locus used in DNA testing

Question 9

What is the probability used in short tandem repeats testing

Answer 9

Random match probability. The probability that two unrelated people will have the same 13 locus DNA profile is between 1 in 200 trillion and 1 in quadrillion

Question 10

Finding a str match

Answer 10

Get this after DNA extraction. DNA causes electrical current to show the sequence base on how far it flys up. The x axis is the number of repeats. Try to use all the same locus. On the y axis and the peaks are measurement of how much genetic material available but open for interpretation. Can show up only one peak instead of two - if person missing one DNA from one parent

Question 11

Error 1: cross contamination

Answer 11

Accidental transfer of cellular material or dna from one sample to another. Can happen at crime scene, in lab, in transfer from station to lab. Produce false reports of a DNS from samples that originated from different people. Can happen w false cold hits. Damaging if there are no suspects.

Question 12

Example of cross contamination

Answer 12

Phantom of Heilbronn
Germany
Mystery women who’s DNa profile was involved in major crimes all da crimes profile everywhere. Couldn’t find this women but her profile was coming up everywhere. 300k bounty for help identifying her. Discovered the women worked at factory that produced cotton swaps for instruments and tool wasn’t wearing gloves to id got everywhere

Question 13

Error 2: mislabelling samples

Answer 13

False DNA incriminations in numerous cases all over the world. New- police incorrectly transferred forensic data to the wrong cases through computer records. Can happen at lab physical mislabel w test table etc. qld - not uncommon for labs to mix up samples from different cases. Can happen in database as well after evidence is recorded.

Question 14

error 2 example

Answer 14

Night stalker
England
140+ sexual assaults serial rapist
Suspect found early in investigation - DNA testing error that switched the reference samples falsely excluded him same name as someone else. Person had solid alibi so changed their mind. Retraced and retesting and found out it was an error.

Question 15

Error 3: misinterpretation of test results

Answer 15

Analysists interpreting wrong results. Especially w not clear cut evidence especially if it’s a mix sample of DNA. Especially if there is more than one perp , suspect more than one but how many do you know? Subjectivity in interpreting DNA mixture: distinguish between male and female etc a lot of interpretation even if you get DNA and

Question 16

Error 3 example: DNA mixture interpretation study 2011

Answer 16

17 qualified DNA analysts to look at DNA evidence from actual case whee answer was know by researcher. Just DNA profile - evaluation of if the man in profile was in the gang rape w other people. They found 12/17 excluded him, 4/17 inconclusive, 1/17 included (same result as actual case).

Question 17

Error 4: gross negligence, scientific misconduct and fraud

Answer 17

Since mid 1990s media exposed lab issues. Eg dry lab bing - creating document and numbers. Mainly a problem in us. Makes finding more consistent w what they think is true making findings more coherent failure to report discrepancies between profiles or problems w controls and labelling info as irrelevant so it doesn’t go to lawyers or jurors

Question 18

How do you detect that can happen

Answer 18

Additional DNA testing
Lab admissions of errors
Issue another report ^
Proficiency testing (catch errors in practices) not published or available
Contamination logs/corrective action files - log all of the problems and detail for later analysis. Not access.

Question 19

Case study: Farah jama

Answer 19

Convicted of raping a women in a nightclub
Swabs taken - tests positive for sperm
No real evidence beside reports of DNA match
Served 5 months in prison - contamination of sample