3 Person example #1

Victim Vaginal SwabVictim and Consensual Partner

“Who Did It”

The Scenario

• Victim hosted a party at her place• She had sex with her boyfriend prior to guests

arriving• She drank too much and went bed before all

guests left • She “dreamed” that someone had sex with

her – boyfriend was still there

The Scenario

• She woke up and ID’d Suspect leaving her room

• Suspect admitted he was in the room, but it was just to grab an X-box game he had left in there

The Egram

Sample Interpretation

• Consistent with 3 persons• Appears to have high- middle- and low-level

contributors• Perhaps the low level contributor drops out?– Some minor alleles <300– Such as our good friend FGA

• X and Y somewhat balanced– Will we be lucky and have Victim as the minor?

The Data Table

Match to Victim

• Victim “fits” every where but FGA• She has a 22 there that is missing from the

mixture• She is the low-level contributor

Match to Consensual

• All alleles of Consensual present• He is 20, 23 at D2 (6 Alleles)• So he is high-level contributor• (State assumption in report)

Match to Suspect

• All alleles of Suspect are found

How many would assume

1. Victim only2. Consensual only3. Victim and

Consensual4. No one

My approach

• I assume both V and C, and will communicate that in the report

• Because V is minor, I’m not concerned about alleles <300, as I know who they belong to

• I have a pretty good idea that C is the major (or at least the majorish)

• I’m interested in the in-between contributor

My approach

• I know we already did the match to the Suspect, but we’ll hide his profile before we start looking at the mixture

• I already decided the mixture is interpretable as a three person mixture, and I have lots of ways to deal with the stat

Any conclusions about Suspect?

1. Match2. Included3. Inconclusive4. Excluded5. None of the above -

Profile cannot be interpreted

The Deconvolution

• We’ll “hide” the Suspect’s type from the table – No peeking!

• Remember to put the calculator into 3 person mode (Not a trivial step)

• Let’s go highest to lowest in terms of number of alleles in our interpretation

• We’ll apply both Victim and Consensual and try to deconvolute Unknown type

• I have to do those 4 things now

The Egram

The Deconvolution

• Start with D2 (six alleles) – And nothing fits!

The Deconvolution

• Recalculate for stutter at D2• Still didn’t help – but I’m smarter than the

software so I’m over ruling it

The Deconvolution

• Why am I going to over rule the computer and make the 17 go with the 24?

• They are both <300 rfu– They are both in the Danger Zone– No requirement for a phr to be >50% if I’m in the

Danger Zone

The Deconvolution

• So if I just lower the phr filter to 40%, they go together

The Deconvolution

• I can now deconvolute that locus and send the results to my new table

• In fact, we get 4 loci with only one option for the Unknown type that auto-graph

• So far:– V = 6%– C = 68%– U = 27%

The Deconvolution

The Deconvolution

• D18 – This is really hard to see, so I apologize – 13, 15 is best (15, 15 P = 14%) (14, 15 phr 59%)

The Deconvolution

• D16 – A homozygote 9 (that’s the only Unknown allele) means 11% Unknown rather than the 20+% we’ve been seeing

The Deconvolution

• D16

The Deconvolution

• D16 – Welcome to the “Not Excluded” option• Even by the “eyeball” method, you can see

that a 9, 11 works well for Unknown

The Deconvolution

• D16 (not excluded) option• Circular or double sharing

The Egram

The Deconvolution

• D16 – Test the “not excluded” option by raising PHR to 70%

• It’s the only thing left – best fit

• But since no P, it can’t graph– (Maybe some day – we’ve got some ideas…)

The Deconvolution

• D5• V = 11, 13• C = 8, 12 (Major)• U= ? (mid level)

The Deconvolution

• D5, U = ? (mid level) – But lots of choices

The Deconvolution

• D5 – mid-level has averaged 27% so far

?

The Deconvolution

• D5 set mP to 5% to get rid of the tiny bits• Also set PHR to 60% to get rid of the option

with the Unknown type being the 89% major contributor

The Deconvolution

• D5 now only 2 choices• I could live with this using the obligate

function, but…. Where’s the fun in that?

• At 70% PHR, the Unknown must be 12, 12– That P of 26% is very nice compared to 27% avg– PHRs for the 2 heterozygous knowns are still OK

The Deconvolution

• D7• V = 7, 10 C = 8, 10• Pretty sure U has a 9

The Deconvolution

• D7 – 9 is in sutter, so correct for it• We’ve learned 50% correction is OK

The Deconvolution

• D7 – What did stutter correction do for us?• We’ve learned from testing that the “true”

combination generally benefits the most from stutter correction

• The “false” combination may not show improvement

• It can be rather subtle• (I’m talking about PHR and P)

The Deconvolution

• D7 – Before correction7,10(phr=98; p=07) 8,10(phr=98; p=79) 9(p=15)

7,10(phr=76; p=06) 8,10(phr=76; p=68) 9,10(phr 76; p=25)

• D7 – After correction7,10(phr=93; p=04) 8,10(phr=93; p=83) (p=13)

7,10(phr=81; p=04) 8,10(phr=81; p=72) 9,10(phr 81; p=24)

The Deconvolution

• D7 – So the stutter correction generally improved the bottom option, and (slightly) “unimproved” the middle option

• At 80% phr, the top (not excluded) option went away

• (I admit the “not excluded” takes some practice samples to get comfortable with)

The Deconvolution

• D7 – My final answer• Because the bottom answer improved the PHR

fairly well and kept the P (24%) of the Unknown right where it’s been (27% avg), I pick 9, 10– I know that both choices have good PHR– I know that I picked the one with the 2nd best PHR– But, I can’t figure out why the enzyme would “miss”

half of the Unknown DNA (I didn’t choose the one with P = 13%)

The Deconvolution

• Where we stand so far:

The Egram

The Deconvolution

• THO1 – V is 7, 9 E is 6, 8• 7, 7 would work great for a mid-level

The Deconvolution

• In fact, at 70% PHR, the Unknown is a 7, 7 (25% of total DNA)• Great PHR for the other two– 100% and 95%

The Deconvolution

• D13• Again, why would I pick an option where ½ the

Unknown DNA just disappeared?

• This tells me he’s not a homozygote here

The Deconvolution

• CSF – Kind of a mess to start with

The Deconvolution

• CSF – But V is the low level, not 39%

The Deconvolution

• CSF – Look carefully at these options

• The top one says Consensual and Unknown together combine to account for 61% - meaning V is 39% - doesn’t make fit

• The bottom one says Victim and Unknown combine to account for 39%

The Deconvolution

• CSF – Quite a few choices, so I really have to study the peak pattern and the known profiles

The Deconvolution

• CSF – This tells me that the Victim is totally masked

The Deconvolution

• CSF• In fact, V’s 6% is probably lost in the expected

variation of the other 2 contributors • Therefore, I will temporarily “un-apply” the

Victim as a required genotype, and treat this as a 2 person locus

The Deconvolution

• CSF • As a 2 person locus, 11, 12 isn’t bad

The Deconvolution

• CSF • Then correcting for 50% stutter pretty much makes it perfect

The Deconvolution

• CSF • So I’ll go back to a three person mixture and

go with an 11, 12

The Egram

The Deconvolution

• D8• V = 14, 14 C = 13, 14

The Deconvolution

• D8 – Change to two person locus as before, Victim + Unknown around 30% so far

• So could Unknown be a 14, 14 (only 14%)?• But the 14 Allele is 8642 rfu (blown out)

The Deconvolution

• D8 – Since 14 allele saturated the detector, we don’t know what the real height is

• A bunch of 14 could still be out there somewhere

• So even though a 14, 14 looks like a low proportion, that’s my call

• (You should probably have an upper limit!)• In our current world I’d have to really argue to

use this injection – this is an old, old sample

The Deconvolution• TPOX• V = 8, 8 C = 8, 11

The Deconvolution• TPOX• 1% for V + U – NO• 99% for C + U – Maybe, but V is pretty good at

D16, D18 and D2 so probably not

The Deconvolution• TPOX• We can “test” by raising PHR• Only 11, 11 remains

The Deconvolution

• D3• V = 15, 16 E = 15, 16• Finally an easy one• 15, 15 (12%) and 16, 16 (1%) don’t work – 15, 16

The Deconvolution

• That leaves FGA• We know V drops out here• So – In the following order:– “Un-apply” V reference (we know the 22 dropped)– “Ignore” the 20 allele (it has nothing to do with

the other two alleles)– Switch to 2 person calculator– (You can always “consider” an allele again)

The Deconvolution

• FGA• Might seem easy – it’s not 1:1• But, this is worst case scenario for stutter!• 24 is very tall, and stutter at FGA = 17%

The Deconvolution

• FGA• So correct for stutter at FGA• Use the 50% we know fits mixtures• 23, 24 for Unknown is 34%, Consensual is 66%

The Deconvolution• We now have a full single source Unknown

profile – no Anys, no Obligates

The Deconvolution

• Graph looks good, but some things don’t graph

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The Stat

• We can’t really use the option from the stat window cause the software remembers a mess– Some loci were converted to 2 contributors– We ignored an allele at FGA– Etc…

The Stat

• But, who cares?• We have a single source profile• 1 in 124 Quintillion

How many of you would…

1 2 3

33% 33%33%

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30

0 of 30

1. Say I was nuts to do that deconvolution?

2. Agree and be OK as my Tech Reviewer?

3. Want to go talk to my Tech Leader about my “interpretation?

How many think…

1 2 3

33% 33%33%

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30

0 of 30

1. I was conservative?2. I was the opposite of

conservative?3. I got the right answer?

Match to Suspect

• I call that an exclusion

• Is it still an “anti-conservative” interpretation if I excluded the guy?

Now What?

• Well, because we excluded this suspect, they sent in another reference from some other guy that was at the party

• This first guy always said that he went in her room, but it was only to get his shoes that he left in there

• So now we’ll bring in Suspect #2’s reference and see how it fits

New Data Table• To cut down on open windows, we’ll do a new

table of the original mixture, the Unknown type and the new reference of Suspect #2

Match to Suspect #2

• Suspect #2 matches the Unknown profile we deconvoluted from the mixture

A Much Faster Way

• Apply all three references, V, C, and S• Set for 3 people• Auto call references• View call report

A Much Faster Way

• Doesn’t graph well – Click through the loci• There are 7 with zero support (no combinations)

A Much Faster Way

• Get on the phone to the investigators and tell them that although all of Suspect’s DNA is found in the mixture, it just doesn’t fit right.

• Can you please send in another reference?• Then apply that new reference to the mixture

and see how it fits

A Much Faster Way

• Still doesn’t graph every where, but we know that (shared types, not excluded, etc)

• But support at every locus (D2 and FGA special)

Things to Consider

• It takes more than just the presence of alleles to be an inclusion

• The inclusion should be supported by all PHR and P expectations – it’s about the math

• I know we’re supposed to look at the mixture without applying the reference, but…

Things to Consider

• If you apply all references and nothing fits, you have an exclusion

• If you apply the references and it all fits, you just did a “real time LR” (sort of)

• But most importantly:

Things to Consider

• Even though we “peeked” at the reference of Suspect #1, it played no role whatsoever in the final interpretation and stat

• If we would have stopped when we saw the result of the first comparison of Suspect #1 to the mixture and just done a CPI, we would have just included an innocent man