JUDICIAL ACCEPTANCE OF DNA PROFILING
John T. Sylvester, J.D.
John H. Stafford, J.D.
DNA Task Force, Legal Counsel Division
Federal Bureau of Investigation
Forensic DNA profiling has been under intense judicial
scrutiny by the courts for over 2 years. (1) Even so, an
overwhelming majority of the courts have admitted forensic DNA
evidence after reviewing it under the varying standards
traditionally afforded novel scientific evidence. In doing so,
the courts have recognized in numerous decisions that genetic
profiles developed from an individuals DNA are reliable,
probative, and objective. (2)
However, despite the many favorable decisions, DNA
evidence, if challenged, must continue to undergo a pre-trial
review, at least until a court of appeals in the jurisdiction in
which the evidence is offered addresses the question of whether
DNA evidence is acceptable. At such hearings, challenges to the
evidence place at issue the ability of the forensic laboratories
to match similar DNA profiles reliably, and thereafter, the
ability to assess the frequency that the matched profile is
expected to occur in the U.S. population. However, it is
anticipated that with the continued strong support of the
scientific community, prosecuting attorneys, and investigators,
DNA profiling will soon be accepted by trial courts as routine
Traditionally, two standards have been used to admit novel
scientific evidence in U.S. courts. Specifically, courts have
adopted either the "Frye standard" or the "relevancy standard"
when deciding whether novel scientific evidence, such as DNA
profiling, will be admitted for use in court. (3)
The "Frye" Standard
Courts applying the "Frye" standard will admit novel
scientific evidence only after it has gained general acceptance
in the pertinent scientific community. (4) Accordingly, the
courts role under "Frye" is more properly limited to an
assessment of the extent to which the scientific community has
embraced the technique as a whole. (5) The analysis performed
in any particular case is not generally at issue in
a "Frye" hearing. (6) Rather, challenges pertaining exclusively
to any one analysis are reserved for the jury, which may place
less weight on the evidence if it concludes that the accepted
testing procedures were not properly applied to the sample in
The Relevancy Standard
As an alternative to the "Frye" standard, many courts have
turned to the "relevancy standard" as the basis for determining
whether the court will accept evidence that arises from new
scientific techniques. The "relevancy standard" is based on the
Federal Rules of Evidence and directs the court to consider the
relevance, (7) the potential for unfair prejudice, and the
reliability of the offered testimony. (8) The general
acceptance of the technique by the scientific community is a
factor in determining the admissibility of new scientific
evidence, but it is not the overriding concern under this
For example, evidence may be rejected under the relevancy
standard, if the jury is asked to accept the expert's bare
assertion on faith alone. (9) In DNA profiling, an
autoradiogram produces a permanent record of the results of this
procedure and is available for review by the defendant and jury.
The danger of a jury being asked to accept a scientific opinion
on faith alone is thereby minimized. (10)
The "Castro" Standard
Recently, a New York trial court in "People" v. "Castro"
(11) expanded these traditional approaches during its review of
DNA evidence. After determining that forensic DNA profiling met
the standards established under "Frye", the court established a
new precedent for the admissibility of DNA profiling evidence,
not just to determine whether the DNA profiling technique is
generally accepted but also to determine whether the technique
was properly applied in the specific case before the court.
The defendant Castro was accused of murder. During the
investigation, investigators obtained a speck of blood from the
suspect's watch. The subsequent DNA analysis performed by a
private laboratory associated the blood with that of the
victim's. However, defense experts disputed the laboratory's
interpretation of the test results, contending that the profile
was uninterpretable or inconclusive.
The court became convinced that the private laboratory did
not properly apply the accepted technique for DNA profiling in
this case and excluded the evidence of a match from use at
trial. Interestingly, the defendant ultimately pled guilty,
admitting the blood on his watch band was that of the victim's.
A few other courts have followed the approach of "Castro".
(12) A party introducing DNA evidence under this standard must
now demonstrate at a pre-trial hearing that the laboratory
properly performed the accepted scientific techniques in
analyzing the forensic samples in the particular case.
Forensic DNA profiling has been reviewed extensively by the
courts under the varying standards afforded novel scientific
evidence, and the number of favorable decisions is encouraging.
An overwhelming majority of courts have admitted forensic DNA
profiling results from the three major laboratories involved in
forensic DNA analysis--the FBI, Cellmark, and Lifecodes. Courts
in at least 49 States have admitted DNA evidence in over 417
hearings and trials. (13) The FBI Laboratory alone has
accounted for admissions in over 120 trials and 85 separate
admissibility hearings in 40 States. (14) Moreover, 23
appellate level courts, including eight State courts of last
resort, have reported favorable decisions after reviewing DNA
profiling under the varying standards of review. (15)
Recently, however, a single State appellate court balked at
recognizing DNA profiling, but left the door open to future
admissions. In "Commonwealth" v. "Curnin", (16) the Supreme
Judicial Court of Massachusetts reversed the trial courts
admission of the DNA evidence analyzed by a private laboratory.
The court observed that the offer of population statistics,
which convey to the jury how common or rare the reported DNA
profile is in the U.S. population, was not supported by
testimony from an expert on population genetics. In the absence
of such testimony, the prosecution could not demonstrate the
general acceptance of the private laboratorys statistical
approach to DNA analysis. (17)
Moreover, the court concluded that without the population
statistics, the jury could not assess the significance of a DNA
profile match. Therefore, the court excluded the evidence of
the match as well. However, the court stated that it will
consider evidence derived from DNA profiling in the future,
assuming the offer of the population statistics is properly
supported by testimony from an expert qualified in the field of
population genetics. (18)
A very few unreported trial court decisions have also
rejected DNA profile evidence offered in a criminal proceeding.
(19) These courts have rejected DNA evidence for differing
reasons, to include the existence of some dissent in the
scientific community over some aspects of the approach to
population statistics and the complexity of the evidence.
However, the rulings that reject DNA evidence because of some
divergence in the scientific community are clearly not
consistent with the standards established by "Frye". Because
"Frye" requires only that the scientific technique be generally
accepted in the scientific community, (20) some divergence in
the scientific community is expected. (21) These isolated
adverse decisions have not generally been followed by other
courts in the same jurisdictions that have admitted DNA evidence
in criminal trials. (22)
In a few other cases, trial and appellate courts have
accepted testimony that two DNA profiles are consistent or
"matched," but then prevented the examiner from producing
population statistics that would convey a sense of how rare the
resultant profile is in the community in which the crime
occurred. The examiner was allowed, however, to express an
opinion on how rare or common the profile is based on the
examiners experience. These courts, in excluding testimony on
population statistics, have voiced concern that such evidence
might have a potentially exaggerated impact on the trier of
"United States" v. "Jakobetz"
While no Federal appellate court decisions currently
address whether forensic DNA profiling is judicially accepted,
two of the more significant challenges to the forensic use of
DNA profiling have been heard by two U.S. district courts. (24)
The first published Federal opinion addressing the admissibility
of the FBI's DNA test results was in "United States" v.
In "Jakobetz," the suspect was charged with kidnaping in
the U.S. District Court in Vermont after he abducted the victim
from an interstate rest area in Vermont, raped her, and then
released her in New York. The DNA profile of semen obtained
from the victim matched the DNA genetic profile of the suspect.
The defense in "Jakobetz" raised a substantial challenge to
the admissibility of the forensic DNA evidence, attacking the
reliability of the FBI Laboratorys procedure, as well as the use
of population statistics in the interpretation of the match.
The population statistics produced by the FBI Laboratory
indicated that the DNA profile of the defendant was extremely
rare and was expected to occur only once in every 300 million
persons. In a 35-page opinion finding general acceptance of the
FBIs entire approach to forensic DNA testing, the court admitted
the DNA profile for use by the jury, noting that the FBI used
"fail-safe" characteristics in its approach to the population
statistics that "redound to the defendants benefit." (26)
"United States" v. "Yee"
The most hotly contested DNA admissibility hearing held to
date occurred in "United States" v. "Yee." (27) The victim in
"Yee" was shot 14 times at close range in his own van. He was
apparently mistaken by his assailants as the leader of a rival
gang. Blood enzyme tests on blood stains recovered from the van
revealed that some of the blood was not consistent with that of
the victim's, leading investigators to theorize that one or more
of the rounds fired into the van ricocheted, hitting one of the
A DNA profile analysis performed by the FBI Laboratory
comparing the blood recovered from the van and that of one of
the defendant's resulted in a match. After a 6-week hearing,
the U.S. magistrate issued a 120-page opinion recommending that
the FBI's DNA test results be admitted.
The magistrate based his decision on the requirements of
the "Frye" standard, finding that there is "general acceptance
in the pertinent scientific community that the procedures
developed and implemented by the F.B.I. for determining that the
DNA patterns from a known [i.e., a criminal suspect] source
match with DNA patterns from a `questioned' [i.e., crime scene]
source are reliable."' (28) He concluded also that there is
general acceptance in the pertinent scientific community of the
process used by the FBI in estimating the probability that such
a match would randomly be encountered in the Caucasian
population of the United States. (29)
The U.S. District Court for the Northern District of Ohio
subsequently adopted the magistrate's recommendation, recognizing
the reliability of the evidence. (30) Several States have also
recognized the inherent reliability and probative value of
forensic DNA evidence and have passed statutes deeming it
admissible in criminal prosecutions. (31)
DEFENSE CHALLENGES TO ADMISSIBILITY
Major defense challenges are mounting in duration and
magnitude as defense attorneys seek to counter the potential
impact on the jury of forensic DNA profiling. These challenges
focus on bias, matching, and population statistics.
A few defense experts contend that the forensic test is
biased against the suspect, since the examiner is aware of which
samples the contributor expects will match. However, the fact
is the FBI's DNA test results actually exclude the named suspects
in about one-third of the submitted cases, often when
traditional serological examinations had included the suspect as
the potential source of the sample. (32) These statistics are
similar to those reported by other laboratories performing
forensic DNA analysis.
Experts for the defense still challenge the ability of the
forensic DNA laboratories to determine reliably a match given
the deteriorated or degraded condition of most forensic samples.
They contend that degraded samples cause the markers to shift
during the processing of the sample to an unknown degree,
possibly resulting in a false matching of samples. No court,
however, has found these criticisms to be valid.
The principle focus of current attacks is on the population
statistics reported by the laboratory after a match has been
established. Because the current application of the technology
does not yet exclude one profile from that of every other person
in the world, DNA profiling laboratories sample a portion of the
population to determine how common or rare certain DNA profiles
occur in the population. From these data, the laboratory then
develops a statistical estimate of how frequently a particular
DNA profile is likely to appear in the U.S. population.
A few scientists have testified that the FBI has not
sufficiently addressed the differences among ethnic
subpopulations within a race, and therefore, cannot properly
assess the resultant effect upon the statistical calculations
provided for a match. However, only two trial courts have
accepted the opinions of these experts in FBI Laboratory cases
as representative of any significant part of the scientific
community, and therefore, rejected the population data estimates
provided by the FBI. (33)
However, this objection is not expected to persist. The
great majority of courts reviewing DNA profiling evidence under
the differing standards of review have considered the challenges
to forensic DNA profiling and now recognize the technique as
reliable and generally accepted by the scientific community.
Moreover, the scientific community and the FBI Laboratory have
developed and continue to develop data that are directly
responsive to the issues raised in the pre-trial hearings.
This information continues to be disseminated to the
appropriate community of scientists. As this information is
disseminated more fully, the consensus of the community should
be manifestly more apparent in favor of the FBI Laboratory's
conservative use of population statistics in DNA profiling.
While DNA profiling is fast gaining acceptance by the
courts, investigators should be mindful that forensic DNA
evidence does not yet positively identify the depositor of a
biological sample. It is but one factor of identification and
cannot be relied upon alone to support a determination of
innocence or guilt.
Given the current state of the technology, forensic DNA
analysis is limited to determining whether the known biological
sample from an individual is genetically similar to a questioned
biological sample. Moreover, the relevance of a match or an
exclusion varies depending on the circumstances in each case.
For example, if the statistical probability arrived at by
the examining laboratory is 1 in 70 (i.e., the odds that someone
other than the defendant is the contributor of the sample in a
particular case), the jury will be informed that the DNA
profile, while a match to the defendant, is fairly common in the
sampled community. The inference is that someone other than the
defendant, even in a small community, could have been the
contributor of the sample. Therefore, the association of the
suspect and the crime scene sample will not be as strong as when
the statistics indicate the profile is more rare. Accordingly,
investigators cannot discount the need for traditional
investigation to support a case for prosecution.
Also, investigators must be aware of the limitations of DNA
analysis that will impact on the decision of whether a person
should be excluded as a suspect in the crime. For example, a
woman is raped, and some semen is recovered. But, suppose the
DNA profile of the semen recovered does not match the DNA
profile of the suspect. Is the suspect exonerated? Perhaps
Consider, for example, that the victim may have had recent,
consensual sexual relations with her husband or a boyfriend
before the rape occurred. The husband or boyfriend of the
victim may be the sole contributor of the sample taken from the
victim immediately after the rape, if the person responsible for
the rape did not contribute a semen sample of evidentiary value.
Consequently, the forensic DNA profile will not match the
suspect's profile, but the absence of the suspect's DNA does not
exclude the suspect.
Accordingly, when additional (non-DNA) evidence gives the
investigator cause to believe that a particular suspect is
responsible for the crime, despite the DNA test results that
suggest the exclusion of the suspect, it is essential for the
investigator to determine whether the victim had consensual
sexual relations before the rape occurred. If so, a DNA sample
should be obtained from that person for comparison to the
A match between the forensic profile and the husband's
and/or boyfriend's profile indicates only that the DNA of the
person believed responsible for the crime was not recovered from
the victim. It follows that the principal suspect cannot be
exonerated as the one who committed the crime on the basis of
the DNA test results.
With few exceptions, Federal and State courts throughout
the United States have overwhelmingly admitted DNA test results,
regardless of the admissibility standard used by the particular
jurisdiction. The RFLP (Restriction Fragment Length
Polymorphism) technique, along with other newly emerging DNA
technologies, has already begun to revolutionize personal
identification in criminal cases.
As the courts continue to recognize the reliability and
probative value of DNA evidence, the public will benefit greatly
from increased efficiency of criminal investigations and trials.
At some point in the not too distant future, DNA evidence will
be routinely admitted in criminal trials and will become as
common as the use of fingerprints. Moreover, advances in
technology will allow for unique identification of suspects
based on their genetic profiles, putting to rest entirely many
of the criticisms based on the limitations of the current
(1) See People v. Wesley, 533 N.Y.S.2d 643 (Sup. Ct. 1988)
(the first reported decision passing on the admissibility of
forensic DNA profiling).
(2) State v. Wimberly, 467 N.W. 2d 499 (S.D. 1991); State
v. Smith, 807 P.2d 144 (Kansas 1991); State v. Pennington, 327
N.C. 89, 393 S.E.2d 847 (1990); Caldwell v. State, 260 Ga.
278, 393 S.E.2d 436 (1990); State v. Ford, 392 S.E. 2d 781 (S.C.
1990); Spencer v. Commonwealth, 240 Va. 78, 393 S.E.2d 609
(1990) (Spencer IV)(PCR); Spencer v. Commonwealth, 238 Va.
563, 385 S.E.2d 850 (1989)(Spencer III); Spencer v.
Commonwealth, 238 Va. 295, 384 S.E.2d 785 (1989) (Spencer II),
cert. denied, ___ U.S.___, 110 S.Ct. 1171, 107 L.E.2d 1073
(1990); Spencer v. Commonwealth, 238 Va. 275, 384 S.E.2d 775
(1989) (Spencer I), cert. denied, ___ U.S. ___, 110 S.Ct. 759,
107 L.E.2d 775 (1990); State v. Schwartz, 447 N.W.2d 422 (Minn.
1989); State v. Woodall, 385 S.E.2d 253 (W.Va. 1989); State v.
Blair, No. 2659, Slip op., unpublished (Ohio App. December 24,
1990); State v. Lee, No. 90CA004741, Slip. op., unpublished
(Ohio App. December 5, 1990); Vickers v. State, 801 S.W.2d 214
(Tex. App. 1990); Snowden v. State, 574 So.2d 960 (Ala. Crim.
App. 1990); Mandujano v. State, 799 S.W.2d 318 (Tex. App.
1990); Lopez v. State, 793 S.W.2d 738 (Tex. App. 1990); State v.
Pierce, No. 89-CA-30, unpublished (Ohio App. July 9, 1990);
Kelly v. State, 792 S.W.2d 579 (Tex. App. 1990); Perry v.
State, 568 So.2d 339 (Ala. Crim. App. 1990); Glover v. State,
787 S.W.2d 544 (Tex. App. 1990); Andrews v. State, 533 So.2d
841 (Fla. 5th Dist. Ct. App. 1988); Martinez v. State, 549
So.2d 694 (Fla. 5th Dist. Ct. App. 1989); Cobey v. State, 80
Md. App. 31, 559 A.2d 391 (1989), cert. denied, 317 Md. 542,
565 A.2d 670 (1989); United States v. Yee, 134 F.R.D. 161 (N.D.
Ohio 1991); United States v. Young, 754 F.Supp. 739 (D.S.D.
1990); United States v. Jakobetz, 747 F.Supp. 250 (D.Vt. 1990);
State v. Pennell, 584 A.2d 513 (Del. Super. Ct., 1989); People
v. Shi Fu Huang, 145 Misc.2d 513, 546 N.Y.S.2d 920 (Sup. Ct.,
1989); People v. Castro, 144 Misc.2d 956, 545 N.Y.S.2d 985 (Sup.
Ct., 1989); People v. Wesley, 533 N.Y.S.2d 643 (Sup. Ct., 1988).
(3) See Giannelli, "The Admissibility of Novel Scientific
Evidence: Frye v. United States, a Half-Century Later,"80
Colum.L.Rev. 1197, 1200-01 (1980); United States v. Downing,
753 F.2d 1224, 1234 (3d Cir. 1985).
(4) Frye v. United States, 293 F. 1013, 1014 (D.C. Cir.
(6) United States v. Gwaltney, 790 F.2d 1378, 1382
(9th Cir. 1986).
(7) See Fed. R. Evid. 401-403, 702-704.
(8) United States v.Williams, 583 F.2d 1194, 1198 (2d Cir.
1978), cert. denied, 439 U.S. 1117, (1979); United States v.
Jakobetz, 747 F.Supp. 250, 254-55 (D. Vt. 1990).
(9) United States v. Downing, 753 F.2d 1224, 1234 (3d
(10) People v. Castro, 144 Misc. 2d 956, 545 N.Y.S. 2d
985 (Sup. Ct. 1989).
(11) Id. at 987.
(12) State v. Schwartz, 447 N.W.2d 422 (Minn. 1989);
Caldwell v. State, 260 Ga. 278, 393 S.E.2d 436 (1990).
(13) See Congress of The United States, Office of
Technology Assessment, Genetic Witness Forensic Uses of DNA
Tests, July 1990, at 157 (hereinafter referred to as OTA).
(14) Personal communication, DNA Analysis Unit, FBI
Laboratory Division, April 30, 1991.
(15) Supra note 2.
(16) Commonwealth v. Curnin, 409 Mass. 218, 565 N.E.2d
(17) Id. at 443.
(19) See, e.g., State v. Wheeler, No. C89-0901 (Or.
Super. Ct., Washington County, March 8, 1990); State v.
Despain, No. 15589, slip op. (Ariz. Cir. Ct., Yuma County,
February 12, 1991); State v. Fleming, No. 90-CR-2716, slip op.
(Ill. Cir. Ct., Cook County, March 12, 1991) (the decision is a
consolidation of two rape cases Fleming and State v. Watson, No.
90-CR-5546, where the DNA admissibility hearings were combined).
(20) People v. Castro, 144 Misc. 2d 956, 545 N.Y.S.2d 920;
see also United States v. Yee, 134 F.R.D. 161 (N.D. Ohio 1991).
(21) United States v. Yee, 134 F.R.D. 161; Commonwealth v.
Lykus, 327 N.E. 2d 671 (Mass. Sup. Ct. 1975).
(22) Subsequent to Wheeler, supra note 19, FBI DNA test
results were admitted in the same county in State v. Herzog,
Nos. C89-0738, C890739, C890691 (Or. Super. Ct., Washington
County, admitted on May 4, 1990). Prior to Despain, supra note
19, FBI DNA test results were admitted in State v.
Medina-Gonzalez, No. CR27078 (Ariz. Super. Ct., Pima County,
admitted on November 27, 1990). Since Fleming, supra note 19,
FBI test results were admitted in Illinois in People v.
Stremmel, No. 90-CF-1024 (Ill. Cir. Ct., Winnebago County,
admitted on May 2, 1991); See also State v. Mehlberg, No.
89-CF-61 (Ill. Cir. Ct., Montgomery County, admitted on August
31, 1990); State v. Smith, No. 90-CF-42 (Ill. Cir. Ct., Ogle
County, December 6, 1990). DNA test results have also been
admitted in Oregon, Arizona, and Illinois by Lifecodes and
Cellmark. See OTA, supra note 13, at 158-172 for listing of
State DNA admissions.
(23) See, e.g., Caldwell, supra note 12 (Lifecodes
statistics reduced); State v. Pennell, 584 A.2d 513 (Del. Super.
Ct. 1989) (Cellmarks statistics excluded); People v. Wesley, 140
Misc.2d 306, 533 N.Y.S.2d 643 (1988)(Lifecodes statistics
reduced); United States v. Martinez, No. CR90-10021-01,(D.S.D.,
testimony on January 9, 1991) (statistics prejudicial based on
prongs set forth in the now vacated Two Bulls decision); State
v. Nelson, No. IK89-09-0882 slip op. (Del. Super. Ct., Kent
County, December 4, 1990) (statistics potentially prejudicial
and confusing to jury); State v. Jobe, No. 88903565, slip op.
(Dist. Ct., Hennepin County, Minn., September 6, 1990)
(statistics of individual allele frequencies admitted but
statistics derived from multiplication of frequencies disallowed
because of previous State supreme court decision discouraging
the use of statistics because of their prejudicial effect).
(24) United States v. Yee, supra note 2; United States v.
Jakobetz, supra note 2; but see United States v. Two Bulls, 918
F.2d 56 (8th Cir. 1990)(ruling vacated 2-21-91 en banc review
granted) rejected DNA evidence using the criteria from the
Castro decision. However, as noted, the Eighth Circuit Court of
Appeals has since vacated the opinion. Moreover, no review of
the decision will be forthcoming from the court as Mr. Two
Bulls recently died.
(25) United States v. Jakobetz, 747 F. Supp. 250, 254-55
(26) Id. at 256.
(27) United States v. Yee, 134 F.R.D. 161 (N.D. Ohio 1991)
(order affirming magistrates recommendation, with addendum for
magistrates recommendation); United States v. Yee, No.
3:89CR720, slip op. (N.D. Ohio, February 1, 1991)(order denying
defendants motion for rehearing on DNA admissibility); United
States v. Yee, 129 F.R.D. 629 (N.D. Ohio 1990)(magistrates
(30) United States v. Yee, 134 F.R.D. 161.
(31) Ind. Code 35-37-4-10 (1990); La. Rev. Stat. Ann.
15:44 1.1 (West 1991); Nev. Rev. Stat. 56.020 (1989); Md. Cts.
& Jud. Proc. Code Ann., 10-9 (1989); Minn. Stat. 634.25-.26
(1990); Va. Code Ann. 19.2-270.5 (1990).
(32) Personal communication, DNA Analysis Unit, FBI
Laboratory, May 4, 1991.
(33) See State v. Despain, No. 15589, Slip. op. (Cir.
Ct. Yuma County, Ariz. February 12, 1991) and State v. Watson,
No. 90-CR-5546, Slip. op. (Cir. Ct. Cook County, Ill. March 12,