🧪 Dna Mixture Statistics
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Dna Mixture Statistics

54 items · 54 forensic · 35 with detail pages

Mixed DNA frequency statistics became the trial's defining forensic dispute. Prosecution experts Dr. Bruce Weir and Gary Sims produced probability calculations from Bundy blood drops and Bronco samples, arguing the matches proved identity. Defense attorneys Peter Neufeld and George Clarke mounted a systematic challenge to the statistical assumptions, backed by a letter from 25 scientists contesting independence calculations. Whether those calculations were sound determined whether the DNA evidence was definitive or unreliable.

Detailed entries (35)

Defense Nanogram DNA Bar Chart (Defense 1165)
🧪 Forensic

A defense chart showing estimated nanogram quantities of high-molecular-weight human DNA across Bundy blood drop items (47, 48, 49, 50, 52) and rear gate sample 117, illustrating the elevated DNA concentration in sample 117 relative to the Bundy drops. Referenced during Gary Sims's testimony and Dr. Gerdes's testimony.

Defendant's 1165Defense 11651165
3 procs · 4 people
1992 NRC Report 'DNA Technology in Forensic Science'
🧪 Forensic

The National Research Council's 1992 report 'DNA Technology in Forensic Science,' published by the National Academy of Sciences. Referenced extensively at trial for its recommendations on the ceiling principle, laboratory error rates (page 88–89), PCR contamination risks (pages 65–67), and mixture frequency assignment methodology (page 59). Defense exhibits Defense 1299 (page 89 excerpt) and Defense 1312 (PCR kits slide) are physical extracts from this report.

Defense 1299Defense 1312
21 procs · 15 people
Dr. Weir's June 21, 1995 Expert Report on DNA Frequencies
🧪 Forensic

Dr. Bruce Weir's 48-page expert report dated June 21, 1995, covering single-stain and mixture frequency calculations for both Cellmark and DOJ results. Admitted as People's 408. The report's Table 29-C (page 38) showed a 1-in-71 mixture frequency; page 2–3 stated Weir assumed validity of DNA profiling by Cellmark, DOJ, and FBI but notably omitted LAPD.

People's 408Exhibit 408
7 procs · 4 people
Letter from ~25 Scientists Challenging DNA Statistical Assumptions (Defense 1145)
🧪 Forensic

A five-page letter signed by approximately 25 scientists in statistics and population genetics, challenging independence assumptions used in forensic DNA frequency calculations and criticizing the product rule. Submitted to Nature magazine (rejected for publication) and marked as Defendant's/Defense 1145 in the criminal trial. A separate but related letter signed by 25 scientists was referenced without an exhibit number in criminal d102.

Defendant's 1145Defense 1145
4 procs · 3 people
Bundy DNA Frequency Statistics Board (Defendant's/Defense 259)
🧪 Forensic

A board or chart displaying DNA typing results and population frequency estimates for Bundy walkway blood drop items 47 through 52. Used by the defense during Robin Cotton's cross-examination and referenced again during Dr. Gerdes's testimony.

Defendant's 259Defense 259
2 procs · 4 people
Civil Trial Weir Mixture Frequency Summary Table (2231)
🧪 Forensic

Dr. Bruce Weir's 'Summary of Mixture Frequencies' document, providing statistical frequency calculations for mixed DNA stains from items 31, 303, 304, and 305 in the civil trial. The most recent version, generated the morning before Weir's testimony, was marked by both plaintiff and defendant as Exhibit 2231.

Plaintiffs' 2231Defendants' 2231
2 procs · 3 people
Defense DNA Concentration Comparison Charts (Defense 1192-A and 1192-B)
🧪 Forensic

Defense-prepared charts comparing DNA concentration (nanograms per milligram) across samples — rear gate sample 117 versus Bundy walkway drops versus Rockingham drops. Introduced and displayed to the jury in criminal proceedings; Gary Sims confirmed the math was substantially correct.

Defense 1192-A and 1192-B1192-A and 1192-B
2 procs · 4 people
DNA Quantification Chart (People's 287)
🧪 Forensic

A chart of DNA quantification (nanograms per milligram swatch) prepared by Gary Sims, showing relative DNA amounts across evidence items 47, 48, 49, 50, 52 (Bundy walkway), 6, 115, 116, and 117 (rear gate). Marked for identification during criminal trial testimony.

People's 287People's 287 (for identification)
2 procs · 2 people
Left-Hand Rockingham Glove (People's 9) DNA Mixture Data
🧪 Forensic

DNA mixture data for the left-hand glove recovered at Rockingham (People's 9), showing results consistent with a mixture of Ron Goldman, O.J. Simpson, and Nicole Brown Simpson. Discussed during criminal trial proceedings when Harmon attempted to link its presence in the Bronco to the console DNA results.

People's 9People's 9 (Glove)
1 proc · 2 people
Prosecution DNA Frequency Board — Main Chart (People's 260)
🧪 Forensic

The prosecution's primary DNA frequency board (People's 260), displaying DNA typing results and population frequency data for multiple evidence items including Bronco samples (steering wheel, console, item 30), formatted to show the percentage or frequency of the population not excluded. Referenced by multiple witnesses across numerous criminal trial proceedings.

People's 260
6 procs · 8 people
Dr. Speed's Letter to Bruce Weir, September 29, 1992 (People's 577)
🧪 Forensic

A letter from Dr. Terry Speed to Dr. Bruce Weir dated September 29, 1992, criticizing the assumptions of the NRC panel with 'sarcasm intended.' Used by the prosecution to impeach Speed's criminal trial testimony.

People's 577
2 procs · 2 people
'Frequencies Most Favorable to Defense' Table (Defendants' 2233)
🧪 Forensic

A civil trial document titled 'Frequencies Most Favorable to Defense — Dr. Weir,' listing stain items with civil trial DNA frequency numbers calculated under assumptions most favorable to the defense. Used to cross-reference Weir's testimony.

Defendants' 2233
1 proc · 2 people
Blood Type and Genetic Marker Frequency Chart (People's 24, Preliminary Hearing)
🧪 Forensic

A chart listing blood types and genetic marker frequencies for three individuals — O.J. Simpson, Nicole Brown Simpson, and Ron Goldman — used at the preliminary hearing to identify which individuals fall within the 43% population frequency for item 49.

People's 24
1 proc · 2 people
Bundy Foyer Blood (Item 12) DNA Frequency Statistics
🧪 Forensic

Civil trial DNA frequency evidence for blood collected from the Bundy foyer, designated Item 12. Robin Cotton testified to a frequency of 1 in 1.2 billion using the African American database, based on only two individuals tested for all five probes—a limitation challenged by defense.

Item 12
1 proc · 1 person
Civil Trial DNA Nanogram Quantities Chart (Defendants' 987)
🧪 Forensic

A chart illustrating nanogram quantities of DNA, introduced during Dr. Gerdes's civil trial testimony to illustrate the scale of DNA amounts involved in the case. Displayed briefly and then removed.

Defendants' 987
1 proc · 2 people
Defense Chart Listing DNA Contamination Scenarios (Defendant's 1144)
🧪 Forensic

A defense-prepared chart listing alternative explanations for the DNA results in the case, including contamination scenarios, coincidental match, and other challenges to the prosecution's interpretation. Introduced during Robin Cotton's criminal trial cross-examination.

Defendant's 1144
1 proc · 2 people
Defense Mixture Frequency Methodology Chart (Defense Chart 410)
🧪 Forensic

A defense-prepared chart summing genotype frequencies for mixture contributors per the NRC report's recommended method, used to contest Dr. Weir's mixture frequency calculation approach during criminal trial proceedings.

Defense Chart 410
1 proc · 2 people
DNA Evidence Showing Unidentified Fourth Contributor (People's 84A and 84B)
🧪 Forensic

DNA evidence (People's 84A and 84B) that could not be matched to Nicole Brown Simpson, Ronald Goldman, or O.J. Simpson, suggesting the presence of an unidentified contributor. Read into the record by Cochran during criminal trial opening proceedings.

People's 84A and 84B
1 proc · 1 person
DNA Small Amounts Comparison Chart (Chart 207)
🧪 Forensic

A demonstrative chart comparing the size of a penny, 20 nanograms, and 2 nanograms of DNA (invisible to the naked eye), used during criminal trial proceedings to illustrate the minute scale of the DNA samples at issue.

Chart 207
1 proc
Dr. Elizabeth Thompson's Letter on DNA Statistics (Defense 1205)
🧪 Forensic

A five-page letter by Dr. Elizabeth Thompson, shown to Dr. Weir during criminal trial cross-examination. Weir confirmed he had seen the letter before. Introduced as Defense 1205.

Defense 1205
1 proc · 2 people
Dr. Weir's New Mixture Frequency Chart on Redirect (Defense 1216)
🧪 Forensic

A chart of new mixture frequency calculations presented by Dr. Weir during redirect examination in the criminal trial, marked for identification during recross-examination as Defense 1216.

Defense 1216
1 proc · 2 people
Earlier Version of Civil Trial Weir Frequency Table (Defendants' 2232)
🧪 Forensic

An earlier version of Dr. Weir's civil trial DNA mixture frequency table, generated earlier in the week of testimony, showing 1 in 200 billion rather than the 1 in 300 billion figure in the updated version. Introduced and compared side-by-side with Defendants' 2231.

Defendants' 2232
1 proc · 2 people
Evett et al. Article on Interpreting Mixed DNA Profiles (People's 411)
🧪 Forensic

Published scientific article titled 'A guide to interpreting single locus profiles of DNA mixtures in forensic cases' by Evett et al., addressing methodology for DNA mixture frequency calculation in forensic contexts. Admitted into evidence during Dr. Weir's criminal trial testimony.

People's 411
1 proc · 2 people
Full Cellmark Genotype Frequency Table (Defendant's 1201)
🧪 Forensic

A comprehensive table of Cellmark genotype frequencies across Caucasian, African American, and Hispanic population databases, introduced by the defense and used as a reference framework during Dr. Weir's criminal trial cross-examination.

Defendant's 1201
1 proc · 2 people
Harmon Letter to Dr. Gary Mullis (Court's Exhibit No. 1)
🧪 Forensic

A letter from prosecutor Rockne Harmon to Dr. Gary Mullis dated June 21, 1995, with an attached letter dated February 2nd and a two-page transcript from another case. Made a court exhibit for the record during a criminal trial hearing.

Court's Exhibit No. 1
1 proc
Neufeld Handdrawn Mixture Frequencies Chart (Defense 1208)
🧪 Forensic

A mixture frequencies chart drawn by defense attorney Peter Neufeld during cross-examination of Dr. Weir, containing three columns including one labeled 'NRC' with frequencies as low as 1 in 2 or 1 in 4. Challenged by Weir as not correctly calculating the frequency of the full evidentiary profile.

Defense 1208
1 proc · 2 people
November DNA Frequency Board (People's 272-B)
🧪 Forensic

The November frequency board (People's 272-B), a prosecution exhibit displaying DNA frequency data that Barry Scheck displayed during a criminal trial sidebar. Referenced during Dr. Weir's testimony in criminal proceedings.

People's 272-B
1 proc · 2 people
Prosecution Mixture Frequency Chart (Prosecution Chart 409)
🧪 Forensic

A prosecution-prepared chart showing the DNA mixture frequency for the Bronco stain calculated as the product of two contributor genotype frequencies, yielding approximately 0.15%. Displayed during Dr. Weir's criminal trial testimony and contrasted with the defense chart.

Prosecution Chart 409
1 proc · 2 people
Prosecution Mixture Frequency Ratios Chart (People's 410)
🧪 Forensic

A prosecution chart displaying frequency ratios for a mixed DNA stain, displayed on the ELMO projector during Dr. Shields's criminal trial testimony.

People's 410
1 proc · 2 people
Steering Wheel Mixture Genotype Frequency Table (Defendant's 1202)
🧪 Forensic

A defense exhibit presenting an extracted table of genotype frequencies for individuals who could contribute to the Bronco steering wheel DNA mixture. Introduced and discussed during Dr. Weir's criminal trial cross-examination.

Defendant's 1202
1 proc · 2 people
Steering Wheel Mixture Population Frequency Summary Slide (Defendant's 1204)
🧪 Forensic

A defense slide summing population frequencies of potential contributors to the Bronco steering wheel DNA mixture, broken down by ethnic database. Introduced and discussed during Dr. Weir's criminal trial cross-examination.

Defendant's 1204
1 proc · 2 people
Dr. Weir's Pre-June 1995 Draft Criminal Trial Reports
🧪 Forensic

A series of draft expert reports by Dr. Bruce Weir submitted to the court before June 1995, including a February 1995 report, a May 11 draft, a May 31 draft, and a June 20 draft—all presenting likelihood ratios for DNA mixtures rather than the frequency approach ultimately used in his final June 21 report. Cited by defense as evidence of shifting methodology.

3 procs
Bronco DNA Mixture Statistical Analysis (Item 78)
🧪 Forensic

Statistical analysis of DNA mixture samples collected from the Ford Bronco, identified as Item 78, showing results consistent with a mixture of O.J. Simpson, Ron Goldman, and Nicole Brown Simpson. The four-contributor blood mixture frequency calculations were disputed by defense, who sought underlying data but received only a summary range.

3 procs · 2 people
Dr. Weir's Revised Frequency Report (During Criminal Trial)
🧪 Forensic

A revised frequency report by Dr. Bruce Weir delivered during criminal trial proceedings—partially received the morning of the hearing—presenting DNA mixture statistics in frequency format. Defense objected that the report repackaged likelihood ratios as frequencies; William Shields testified it departed from NRC methodology.

2 procs · 2 people
Second NRC Report (1996) on Forensic DNA Statistics
🧪 Forensic

The National Research Council's second report on forensic DNA evidence (1996), which abandoned the ceiling principle recommended in the 1992 report and endorsed the product rule for calculating DNA profile frequencies. Referenced in civil trial testimony by Gary Sims.

2 procs · 3 people

Additional references (19)

Brief references from transcripts that don't warrant an individual page. Each has a single source or is mentioned only in passing.

  • 1992 Cellmark DNA Population Database — The 1992 Cellmark Diagnostics DNA population database, described at criminal trial as the only Cellmark database formally in evidence via Robin Cotton's testimony.
  • 1994 Cellmark DNA Population Database — The 1994 Cellmark Diagnostics DNA population database, referenced by Dr. Weir in his February 1995 report. Its admissibility was challenged by defense as lacking foundation; prosecution argued Weir's close collaboration with Cellmark permitted reliance.
  • Cellmark and DOJ Written Reports with Frequency Estimates — Written reports from Cellmark Diagnostics and the California Department of Justice providing DNA frequency estimates for the case, received and reviewed by Dr. Weir as part of his criminal trial expert analysis.
  • Department of Justice DNA Statistical Reports — The California Department of Justice's DNA statistical reports for this case, discussed during Dr. Weir's criminal trial cross-examination. Weir confirmed the DOJ does not report confidence limits in its statistical reporting.
  • DNA Bloodstain Testing Results — Jury Instruction Discussion — DNA bloodstain testing results and associated laboratory error rates and frequency estimates discussed in the context of criminal trial jury instructions, resulting in the court adding two sentences on lab error rate language to special instruction no. 3.
  • DNA Match Statistics (1 in 57 Billion to 1 in 150 Billion) — DNA match statistics of 1 in 57 billion to 1 in 150 billion, cited by Gary Sims during civil trial testimony as the overall frequency range for the DNA evidence in this case.
  • Dr. Bruce Weir Preliminary Memo on Mixed Sample Frequencies (Criminal d73) — A preliminary memo by Dr. Bruce Weir containing mixed sample frequency calculations, discussed in criminal trial proceedings before his formal expert report was complete. Described at the time as lacking sufficient data, calculations, and article citations.
  • FBI Population Frequency Databases (Used by California DOJ) — FBI population frequency databases used by the California Department of Justice for RFLP frequency calculations in this case. Discussed during Dr. Weir's criminal trial testimony; Weir confirmed DOJ relied entirely on FBI databases for its RFLP calculations.
  • FBI World Population Study (HAE 3 Restriction Enzyme Data) — An FBI world population study containing HAE 3 restriction enzyme population data used to calculate DNA profile frequencies. Discussed during Gary Sims's prosecution testimony in the criminal trial; Harmon attempted to introduce it while Scheck objected on scope grounds.
  • LAPD Lab PGM Sub-Type General Population Frequency Chart (Preliminary Hearing) — An LAPD laboratory frequency chart for PGM sub-type providing general population data not broken down by race, discussed during criminalist Greg Matheson's testimony at the preliminary hearing.
  • List of NRC Committee Members — A list of members of the NRC committee that produced the 1992 'DNA Technology in Forensic Science' report, reviewed by Dr. Speed on the stand during criminal trial proceedings.
  • Matheson Blood Type Frequency Calculation (1 in 200) (Preliminary Hearing) — Preliminary hearing testimony by Greg Matheson presenting a frequency calculation: Type A (33.7%) × PGM sub-type 2+2− (1.6%) × Esterase D type 1 (79.6%) = 0.43%, rounded to approximately 1 in 200.
  • Socks Blood Stain DNA Frequency Statistics — DNA frequency statistics for the blood stain found on socks from O.J. Simpson's residence, with calculated frequencies ranging from 1 in 6.8 billion to 1 in 530 billion. Discussed during Robin Cotton's criminal trial testimony; defense challenged whether blood could have been placed on the socks after collection.
  • Table 30 Three-Contributor Calculations (Weir Report) — A table of three-contributor DNA mixture frequency calculations from Dr. Weir's report, referenced during criminal trial proceedings as the model for the format of four-contributor data that the defense sought but did not receive.
  • Tinker Toy DNA Demonstratives (Civil Trial) — Tinker toy models used as demonstratives during DNA argument in the civil trial, admitted over plaintiff's objection.
  • Two-Donor DNA Frequency Report with Potential Pair Counts — A DNA frequency report by Dr. Weir addressing two-donor mixture scenarios, including potential pair counts. Referenced by Peter Neufeld during criminal trial proceedings to illustrate that Weir had performed this analytical step for two donors but not for three or four donors.
  • Weir Article 'DNA Statistics in the Simpson Matter,' Nature Genetics (1995) — A peer-reviewed article by Dr. Bruce Weir titled 'DNA Statistics in the Simpson Matter,' published in Nature Genetics, Vol. 11, December 1995. Used during civil trial cross-examination to challenge Weir's stated methodology and extract admissions about likelihood ratios.
  • Weir Article in 'Advances in Forensic Haemogenetics' — An article by Dr. Bruce Weir published in the journal 'Advances in Forensic Haemogenetics,' discussing mixture frequency calculations for DNA evidence. Turned over at deposition and referenced during civil trial cross-examination.
  • Weir Paper Presented at Promaga Conference (~October 1995) — A paper by Dr. Bruce Weir presented at approximately the October 1995 Promaga Conference, discussing appropriate frequency calculation methods for DNA mixture evidence. Turned over at deposition and referenced during civil trial cross-examination.
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