Version	1	/	Date	of	Issue:	10.29.15	/	Issuing	Authority:	Forensic	Science	Standards	Board	(FSSB)

OSAC	Research	Needs Assessment Form

Title	of	research	need:

Keywords:

Submitting subcommittee(s): Date	Approved:

(If	SAC	review	identifies	additional	subcommittees,	add	them	to	the	box	above.)

Background	information:

1.	 Description	of	research	need:

2.	 Key	bibliographic	references	relating	to	this	research	need:

3a.		In	what	ways	would	the	research	results	improve	current	laboratory	capabilities?

Much	 progress	 has	 been	 made	 for	 the	 analysis	 of	 autosomal	 STR	 mixtures	 including	 the	

development	of	software	solutions	for	mixture	deconvolution	that accommodate	the	probability	of	

allelic	drop	out and	drop	in for low-level	and	degraded	profiles.	Very	little	research	has	progressed	

for	 best	 practices	 for	 the	 deconvolution	 of	 Y-STR	 mixtures and/or	 the	 comparison	 of	 known	

samples	to	Y-STR	mixtures.	This	research	should	specifically	include	work	on	rapidly	mutating	YSTRs	and	male	relatives,	where	a	low	amount	of	discrimination	is	expected.	

(1)	Scientific	Working	Group	on	DNA	Analysis	Methods	Interpretation	Guidelines	for	YChromosome	STR	Typing	(approved	on	January	9,	2014)	-

http://media.wix.com/ugd/4344b0_da25419ba2dd4363bc4e5e8fe7025882.pdf

(2)	Taylor	D,	Bright	J-A,	and	Buckleton	J	(2016)	Using	probabilistic	theory	to	develop	interpretation	

guidelines	for	Y-STR	profiles.	FSI-Genetics 21:22-34.	

(3)	Andersen	MM,	Eriksen	PS,	Mogensen	HS,	and	Morling	N	(2015)	Identifying	the	most	likely	

contributors	to	a	Y-STR	mixture	using	the	discrete	Laplace	method. FSI-Genetics 15:76-83.	

(4)	Ballantyne	KN,	Keerl	V,	Wollenstein	A	et	al	(2012)	A	new	future	of	Forensic	Y-chromosome	

analysis:	rapidly	mutating	Y-STRs	for	differentiating	male	relatives	and	paternal	lineages.	FSIGenetics 6:208-218.

Approximately	60%	of	the	crime	labs	in	the	U.S.	conduct	Y-STR	testing	(Doug	Hares,	NDIS

Custodian, personal	communication).	There	is	very	little	guidance	to	the	forensic	community	on	

how	to	interpret	indistinguishable	mixed	Y-STR	profiles.	The	2014	SWGDAM	guidelines	for	Y-STR	

typing	states,	“SWGDAM	has	not	yet	reached	consensus,	however,	on	the	appropriate	statistical	

approach	for	estimating	the	occurrence	of	a	combination	of	haplotypes	in	a	population.”	Research	

to	understand	the	underlying	behavior	of	Y-STR	mixtures	is	sorely	needed	and	would	allow	

laboratories	to	interpret	and	report	these	mixtures.	

		

Software	solutions	for	Y-STR	mixture	deconvolution

Y-STR	mixtures,	Continuous	Probabilistic	Genotyping,	Likelihood	Ratio

BDIRC 8/25/16
Version	1	/	Date	of	Issue:	10.29.15	/	Issuing	Authority:	Forensic	Science	Standards	Board	(FSSB)

3b.		In	what	ways	would	the	research	results	improve	understanding	of	the	scientific	basis	for	the	

subcommittee(s)?

3c.		In	what	ways	would	the	research	results	improve	services	to	the	criminal	justice	system?

4.		Status assessment	(I,	II,	III,	or	IV):		

This	research	need	has	been	identified	by	one	or	more	subcommittees	of	OSAC	and	is	being	provided	as	an	

informational	resource	to	the	community.

Major gap	

in	current	

knowledge

Minor gap	

in	current	

knowledge

No	or	limited

current	research	

is	being	

conducted

I III

Existing current	

research	is	being	

conducted

II IV

Many	of	the	core	Y-STR	loci	suffer	from	low	resolution	in	a	population	much	like	some	of	the	low	

discriminating	autosomal	loci	(e.g.	TPOX).	Allele	sharing	can	increase	the	uncertainty	of	being	able	

to	determine	the	number	of	contributors.	There	is	no	guidance	on	establishing	mixture	ratios	 for	

the	deconvolution	of	two	(or	more)	mixed	males.	For	example,	is	the	“major”	contributor	at	a	5:1	

ratio	 consistent	 across	 the	 entire	 profile?	 There	 is	 also	 not	 enough	 data	 on	 other	 mixture	

parameters	like	number	of	contributors,	effect	of	degradation,	and	stutter.	Presently,	statistics	for	

Y-STR	mixtures	use	a	counting	method	calculation	of	how	many	individuals	in	the	database	could	

not	be	excluded.	This	approach	could	be	improved	by	pursuing	probabilistic	genotyping.	Software	

solutions	for	deconvoluting	mixtures	and	the	interpretation	of	missing	(drop	out/in	or	the	effect	of	

null	alleles)	data	is	needed. 		

One	advantage	of	Y-STR	testing is	the	usefulness	for	resolving	mixtures	where	there	is	a	high	

female	background	and	low	male	profile	(in	an	autosomal	STR	mixture).	Given	the	focus	on	

processing	untested	sexual	assault	kits,	having	more	research	and	software	tools	to	help	resolve	

multiple	male	contributor	Y-STR	mixtures	would	benefit	the	criminal	justice	system.			

I
Version	1	/	Date	of	Issue:	10.29.15	/	Issuing	Authority:	Forensic	Science	Standards	Board	(FSSB)

// Approval	date:

(Approval	is	by	majority	vote	of	subcommittee.		Once	approved,	forward	to	SAC.)

1.		Does	the	SAC	agree	with	the	research	need?				Yes			X	⃝							No							⃝		

2.		Does	the	SAC	agree	with	the	status assessment?				Yes				X	⃝							No							⃝	

If	no,	what	is	the	status assessment	of	the	SAC:

Approval	date:

(Approval	is	by	majority	vote	of	SAC.		Once	approved,	forward	to	NIST	for	posting.)

Subcommittee 04/24/2016

SAC

08/24/2016