Role and Impact of Forensic Evidence in the Criminal Justice Process

Justice Research and Statistics AssociationOctober 23, 2009

Joseph Peterson, Ira Sommers, Donald Johnson, Deborah Baskin

School of Criminal Justice and CriminalisticsCalifornia State University, L A

Los Angeles, CA

Background

Forensic sciences have seen dramatic scientific breakthroughs in last 25 yearsThe CSI phenomenon has sensitized CJ personnel and public to forensic scienceStill, lab resources have not kept pace with submissions and backlogs >500KMany federal efforts (DNA Initiative, Coverdell Act, etc.) have assisted

Background (continued)

Many professional programs have evolved to elevate quality of forensic lab resultsStill, scandals have shaken crime lab profession (FBI, West Virginia, Houston PD, etc), causing concern over reliability of evidenceU.S. Supreme Court decisions (Daubert, etc.) have named judges as ‘gatekeepers’ to assess quality and reliability of scientific evidenceNational Academy of Sciences panel issued landmark critical report in February 2009

National Institute of Justice Research Solicitation

It has been 25 years since there was an assessment of the uses and effects of scientific evidence on police and courtsAn estimated $1.5 billion is spent annually on forensic services but question remains: What are its uses and impact?NIJ solicited proposals in 2006 to assess the role and impact of forensic services

NIJ Project GoalsDetermine:

Percent of crime scenes with forensic evidenceVarieties of forensic evidence recovered from different categories of major crimesTrack evidence collection, analysis and attrition of evidence from incident thru lab into courtsIdentify types of forensic evidence that contribute most often to successful case outcomes (relative to its availability)

Prevalence of Crime Labs and Scientific Evidence

Presently are about 400 crime laboratories nationwide examining 2.5 M requests annuallyStudies in 1980s found evidence collected in only about 20-30% of cases, varying greatly by offense typeHuge investment in DNA over past five yearsControlled substances (70%) still dominate lab caseloads, followed by biological evidence, firearms and fingerprints

Present NIJ Study

Thirty (30) month project Oct 06-Apr 09

Three study sites selected representing city, county, and state-wide laboratory systems:

Los Angeles County, CA Indianapolis, INIndiana State Police Lab and local jurisdictions of South Bend, Ft. Wayne, and Evansville

Data Collection

Prospective analysis of (2003) official records, data tracking police incidents (into/out of laboratory) to final case dispositionStratified, random sample (homicides, agg. assaults, rapes, robberies, & burglaries) of more than 4,000 incidents selected from police files in each of five study sitesPolice incident, crime scene, investigator, laboratory, prosecutor, and court files reviewed

Critical Decision Points

Crime scene evidence collectionLaboratory acceptance, prioritization and analysis (criminalist, detective, prosecutor)Police decision to investigate, arrest and/or exclude suspectsProsecutor decision to file charges, accept pleas, or take cases to trialFact-finders/pros and defense attorneys use of scientific evidence, reports and testimony

Independent Variables

Key Individual Case-LevelDemographics of suspect/victim, offense type, report/response time, witnesses, information/evidence collected, scientific results, offender and case processing characteristics, key decisions, demographics

Key Dependent VariablesLogistic Regression Analysis

If reported crime led to arrestIf arrest referred to prosecutorIf prosecutor filed chargesManner of disposition (plea/trial)Convict/no convictIf convicted, nature of sentenceLength of sentence

Incidents Randomly Sampled by Jurisdiction (2003*)

LA IN EV FW SB

HOM 245 71 14 38 32

RAPE 231 150 75 70 76

ROBB 528 335 80 73 65

ASSLT 230 323 108 95 103

BURG 489 350 142 144 138

Per Cent Offenses with Crime Evidence Collected

LA(%) IN(%) EV(%) FW(%) SB(%)

HOM 96 97 100 100 100

RAPE 51 73 75 66 72

ROBB 19 28 44 25 35

ASSLT 25 33 26 38 32

BURG 21 23 15 15 16

Phys Evid/Substrates Collected Indianapolis Crime Scenes

HOM (%)

RAPE (%)

ROBB (%)

ASSLT (%)

BURG (%)

Biolog 89 63 0.3 5.3 2

Prints 75 2 16 0.3 20

Fire-arms

82 0.7 7 26 0

Nat/SynMatrls

69 47 0.9 0.3 0.3

Moderate Filtering of Forensic Evidence in Los Angeles

HOM (%)

RAPE (%)

ASSLT (%)

ROBB(%)

BURG (%)

CLLCT SCENE

96 51 25 19 21

SBMIT LAB

92 49 13 8 19

EXAM 80 22 7 7 10

Major Filtering of Evidence in Evansville

HOM (%)

RAPE (%)

ASSLT (%)

ROBB (%)

BURG (%)

CLLCT SCENE

100 75 26 44 15

SBMIT LAB

100 11 8 13 3

EXAM 100 11 8 13 3

Crime Lab Results (Indianapolis)

EXAM (#)

INDIV (#)

+ID (#)

-ID (#)

HITS (#)

HOM 55/56 31 4 8 0

RAPE 25/44 6 11 0 0

ROBB 43/44 32 36 0 0

ASSLT 33/39 14 10 0 1 AFIS

BURG 47/47 35 36 0 4 AFIS

BiVariate Relationships

Cases With/Without Forensic Evidence Collected, Submitted, and Examined

ArrestReferralChargeOutcomeSentence

Arrests Rates for Offenses With and Without Crime Scene Evidence

LA(%) IN(%) EV(%) FW(%) SB(%)

HOM* 46/40 73/100 100/0 47/0 78/0

RAPE 56/50 78/44 25/11 22/8 29/5

ROBB 50/19 45/9 63/16 44/7 35/5

ASSLT 51/71 73/37 75/36 58/20 39/24

BURG 13/9 12/5 29/6 24/6 9/6

Bivariate Relationships: Crime Scene Evidence (Y/N) and Case Progress

(Number of Sites Where Significant*)HOM ASSLT RAPE ROBB BURG

ARRST * *** ** ***** ***

REFRL * * NS * NS

CHRGE

NS * NS ** NS

Cases with Crime Scene Evidence as Significant Predictor of Arrest

Los Angeles - Homicide*, RobberyIndianapolis - Rape, Assault, Robb, BurgEvansville - Assault, Robbery, BurglaryFort Wayne - Assault and RobberySouth Bend - Rape and Robbery

*Firearms, Materials Evidence

Cases Where Crime Scene Evidence Significant Predictor of Arrest -

Fraction Examined Prior to Arrests

ASSLT RAPE ROBB BURG

LA 2/131

INDY 7/158 13/103 9/62 2/23

EVANS 1/50 6/29 1/13

FW 0/33 4/12

SB 1/17 0/10

Explaining Higher Arrest Rates For Cases with For. Evidence, But Not Yet Examined

Are these cases different in fundamental ways?

How/who reports themHow suspects are identified/apprehendedRelationship between victim and suspectDoes physical evidence have immediate value even though not yet examined?Is quantum of proof for an arrest satisfied with presumptive scientific evidence?

Role of Forensic Evidence in Direct vs. Descriptive ArrestsHypothesis: Forensic evidence of greater value in direct observation casesDirect:

Suspect apprehended, admission, suspect surrender, arrest in another case, police observe, traffic stop, recovered property

Descriptive:Vehicular description, citizen observation, photo ID, suspect description, line-up

Combining Smaller Jurisdictions All Part of Indiana State Lab SystemSouth BendFort WayneEvansville

COMBINED INDIANA SITES: FOR EVID PREDICTORS OF ARREST (Sig Level***)

HOM ASSLT RAPE ROBB BURGCrime Scene Evidence *** ** *** **LaboratoryEvidence * *** ***Lab Examine Evidence * *** **Biolog Crime Scene * **Prints Crime Scene ***Biolog Lab Evidence * ***Unique Indi-viduality *** *

Individualized/Associative Lab Results, Arrest and Conviction

Total Arrest Convict Rate

Assault 5/859 3 2 67%

Burglary 18/1263 8 4 50%

Hmicide 80/400 57 46 81%

Rape 16/602 11 9 82%

Robbery 14/1081 11 9 82%

Individualized/Associative Evidence and Conviction Rate

Single Form - 67% (convictions/arrests)20% firearms20% biology57% latent prints

Two or More Forms - 86%29% biology29% firearms14% latents29% combination of above

Total Individualized Evidence By Offense

Assault - Bio/Firearms - 5 casesBurglary - Latent Prints - 18 casesHomicide - Latents, Firearms, and Bio 80 casesRape - Bio/Latents - 16 casesRobbery - Latents - 14 cases

Plea/Trial and Sentencing

Generally, forensic evidence strengthens a case and influences cases to go to trial (Assault, Rape)

Generally, examined forensic evidence leads to more severe sanctions -Assault, Burglary (two jurisdictions)

Citizen Polls and Surveys

Field poll (CA) queries of 1201 randomly selected California registered voters (telephone) as to their views of reliability and importance of forensic evidence and:

Television viewing habitsJury service experience C J employmentCrime victimization

Citizen Poll Regression Results

Citizens generally perceive forensic evidence as much more reliable than other forms of testimonial evidenceCitizens who watch more hours of TV programming regard forensic evidence as more reliable Citizens who watch justice themed TV crime shows were more than twice as likely to convict than those who didn’t

Implications for Policy/Practice

Collection of Physical EvidenceLab Examination of EvidenceInvestigations of CrimesProsecution and AdjudicationCSI Effect

Investigation for and Collection of Physical Evidence

Most scenes have physical evidence and much is collected to insure it does not perish and to comply with modern forensic science expectations Much physical evidence is filtered between crime scene and laboratory analysis - most by crime scene technicians and detectivesFirearms, latent (finger) prints and biological evidence is most often collected and submittedProsecutors play major role in influencing decisions to collect, submit and analyze evidence

Criminal Investigations

Physical evidence adds value and momentum to investigation even before/without lab analysisControlling for other investigative factors, forensic evidence associated with arrest in many casesOther case characteristics (victim and witness reports) are also important predictors of arrest Forensic evidence is valuable at arrest, but less so at subsequent stages of prosecution/adjudicationForensic evidence (latent prints and firearms) from robberies consistently associated with arrest in all study sites

Laboratory Analysis

Most examinations of evidence will await determination that results of analysis are neededA comparatively small percentage of examinations result in individuality of evidence and linkage to suspect/victimInquiry into data bases seldom provide identity of unknown offender

Prosecutions and Adjudications

Prosecutors are very mindful of ‘CSI Effect’ and expectations of court/jurorsCharging decisions are heavily influenced by overall convictability of caseValue of forensic evidence as predictor diminishes after chargingStronger evidence cases, including forensic evidence, more often result in trialSentence/plea bargaining may be influenced by presence of lab analysis and report

Influence of CSI EffectInvestigators and crime scene technicians very aware that arrests and prosecutions may not be sustained unless evidence collected/proper procedures followedProsecutors believe forensic evidence is central to plea and trial convictionProsecutors are pressed to state proper procedures followed in cases, even those lacking forensic evidenceProsecutor view of case needs influences actions of crime scene, investigators and laboratory

Thank you!