Saturday, July 11, 2009

It Is The Jury That Ultimately Matters: How They May Be Seeing The DNA Here

Posted by Fiori

Example of well-equipped Italian DNA lab

Ciao! Posting again from Florence.

Nicki and Kermit have already done amazing work here and here in explaining the hard facts of the DNA evidence.

This post is about perceptions and about what the judges and jury might - might - now be thinking, now that those facts are presented and some of them contested.

DNA evidence is notoriously hard to present and argue before a jury. It is not only in the trial against Amanda and Rafaelle that one finds problems, ambiguities and different interpretations of the validity and reliability of DNA, this is the same in many criminal trials.

Standardization of DNA testing procedures got an enormous boost by the unforeseen “accident” in the OJ Simpson’s trial, where the jury, according to all scientific authorities, failed to recognize the DNA evidence properly. Since than the overall public understanding of DNA has been increasing, and jurors and others agents have earned a familiarity with handling DNA in criminal trials. All this suggests that it is generally getting easier for jurors to understand when and how DNA is significant in a trial.

It is of great importance to underline that the jury is the crux of every case: No matter what Dr. Stefanoni knows and how she may have handled the DNA samples, it is the jury, this particular selection of individuals, which has to make sense of the testimonies, and form an understanding of what the DNA samples tells about the murder of Meredith and the possibly involvement of Amanda and Rafaelle (and Rudy). I emphasize this:

  • Jurors are not a scientific committee, and the way which a jury understands DNA differs considerably from a professional, scientific understanding of DNA

  • Jurors’ understanding of DNA is highly situational; i.e. it is heavily influenced by how, when and by whom DNA material is presented during the trial

  • Jurors build their comprehension from context, meaning that a jury does not base their understanding upon systematically selected information about DNA, but forms an opinion based upon an interrelation of scientifically based information and the circumstances of the present case

Findings from the US and UK system of justice

What characterizes jurors’ judgments of DNA material in criminal trials? It is usual to expect that the more scientifically complex a piece of evidence is, the more difficult is it for a jury to comprehend, but from studies in UK, US and Australia several other things are known:

  • Among jurors who were aware of DNA profiling evidence before their participation in the researched trials, expectations for the evidence in determining the guilt or innocence of an accused were high, and these expectations were largely confirmed by the jury members experiences of the trial itself.

  • Juror comprehension of DNA evidence is not solely dependent on the scientific complexity of the evidence. If the evidence is presented clearly in court, if the expert testimony is consistent, if the defences do not present contrary interpretations of the DNA evidence, and the case is otherwise circumstantial, then jurors seem to manage a fair understanding of the science and weight it significantly in case material.

  • The strength of the defence challenge may depend on the coherence and grounding of an alternative explanation or conclusion drawn from the DNA. Meaning: it is NOT generally so, that IF a piece of DNA evidence is NOT contradicted by the defence, then it is easier for a jury to comprehend DNA evidence. HOW a jury interprets DNA evidence depends upon the context of the PRESENTATION of the evidence.

Research into US trials reports that jurors mostly are much more skeptical toward DNA evidence than statistics gives reason for. The jurors often “incorrectly aggregate separately presented probabilities and afford probabilistic evidence less weight than would be expected [by experts]” and “their background beliefs about the possibility of laboratory errors and intentional tampering affects the weight participants afford a DNA match report.”

A juror’s interpretation of expert testimonies is highly influenced by the credibility they assign to the legal and scientific system; i.e. all the institutions involved in a trial: the police, the legal system, the forensic police, and scientific institutions in general.

The point made here is that jurors and legal systems have “historical memory” so the result of one trial influences the outcome of another:  Thus, it is possibly that the OJ Simpson case and the many faulty convictions based upon DNA ‘evidence’ has produced a overt negative attitude towards DNA in the US, which is not to be expected to be the same in Italy.

Another conclusion, also from research within the US: Cognitive errors favoring the defence were more prevalent than errors ones favoring the prosecution. This piece of research examines how jurors’ evaluates that part of the DNA testimony which involves probabilities and statistics. And as this touches upon core questions brought up in the case against Amanda and Rafaelle, I will quote in length from the paper.

    The paper, which studies the outcome of several (murder) trials - concludes that “some jurors showed susceptibility to classic (defence) fallacies in interpreting conditional probabilities, and the jurors as a group were not overwhelmed by testimony from a prosecution expert that ‘more than 99.98% of all Caucasians would be excluded’ by the DNA match.
    Most jurors accepted a defence criticism of this computation. Moreover, it appears that many jurors were inclined to agree with the defendant’s overstated argument that because dozens of men in the area might have DNA types consistent with those of the robber, the match with the defendant’s DNA was worthless. A smaller number seemed to commit what has been called the ‘prosecutor’s fallacy.’ These jurors did muddle up the proportion of the general population that would be excluded by a DNA test, and the probability that the defendant was the source of the crime-scene DNA.
    On balance, these findings do not indicate that jurors generally were unduly impressed by the prosecution’s DNA evidence. Consequently, our results challenge the legal argument that DNA evidence should be excluded because jurors are prone to overvalue such evidence.”

So, measured in relation to the expert testimony actually given in court, this research found that jurors made misunderstandings and misinterpretations biased BOTH ways. The research did not find jurors to be ‘unduly impressed’ by prosecutions experts testimony, but instead being ‘susceptible’ in favour of the defence. 

But other research indicates that some jurors are being too impressed by the DNA evidence or mislead by the statistics presented in court.

Research from UK and US, states that “a number of convictions which have relied on DNA evidence have been overturned on appeal on the basis of misdirection of the jury regarding the statistical basis of the test and its results. In particular, juries are often awe-struck by the enormous values of random occurrence ratio with which they are presented by the prosecution experts. The factual significance of these large numbers is often misunderstood and misrepresented by barristers and judges, leading to unsafe convictions.”

Then, not only the jurors, but the legal actors more widely have problems with understanding how the statistical dimensions of DNA evidence works. The point of the statistics is, that identifying the DNA markers can be misleading if identification of the suspect occurs on behalf of ‘random occurrence ratios’ – i.e. the suspect is identified in random by her DNA (similar to how fingerprint identification works).

Identification on behalf of DNA must relate to the demography of the area where the crime took place, as well as the family background of the suspect. Meaning that statistics can be misleading if identification is not supported by additional information (where much exists in the trial against Amanda and Rafaelle). Dr. Stefanoni has repeatedly argued this point in court, explaining why Amanda’s DNA is Amanda’s, and Rafaelle’s DNA is Rafaelle’s, and not a ‘random’ person, like an unknown friend of Rudy’s.

From research into the working of the US and the UK legal systems, it must be clear that most of the news-reports from the US about the murder of Meredith Kercher tend to reinforce a common deficit in knowledge on how to interpret DNA evidence. A shame that.

Also worth mentioning is that the OJ Simpson trial is not the only one where ‘scientifically’ obvious DNA evidence have been disregarded by a jury; this also seen in cases where there presented a lot of other circumstantial evidence supporting the DNA material.

And that different interpretation (prosecution and defence) of DNA material does not in itself blur jurors comprehension and prevent an unanimous understanding of the significance. Contrary, controversies over DNA can serve to clarify a juror’s understanding of DNA.

Example of well-equipped Italian DNA lab

Likely differences under the Italian system of justice

These results from research into the US/UK type of legal system should be discussed in relation to the working of the Italian system. And there are, in this perspective, significant differences.

In Italy, a jury consists of 6 lay persons and 2 professional judges. It is highly likely that the participation of 2 professional judges influences how the jury perceives and discusses DNA and other complex scientific matters. The above quoted research into fallacies of comprehending DNA evidence can only support the view that it is a strength of the Italian system that professional judges are represented in the jury.

Also, the Italian trial system, where parts of evidence are presented and assessed by multiple judges in many pre-trial hearings, also marks a difference vis a vis the US system. Every (pre-) trial adds to jurors possibility to comprehend DNA material correct (‘correct’ in relation to understanding what is actually testified in court, not ‘correct’ in relation to assessing the significance of the DNA material as evidence).

As referred to above, pre-trial experiences also influences how jurors interpret DNA testimony.

Then education, schools and general cultural education (‘bildung’ in German), cultural habits (for example if criminal trials are broadcast or not, and if they are watched widely or not) will without doubt influence how jurors comprehend DNA evidence. And of course so will criteria used by the court for selecting the actual jury influence the outcome; for example if it was considered important that jury members demonstrated ability to understand complex scientific arguments.

Generally, European comparative test shows that primary education in Italy are in the upper middle, and Italy has very good universities and strong academic traditions, and – not the least - a long and proud tradition in science from Leonardo da Vinci and onwards.

These conditions will influence the jury’s assessment of DNA evidence presented in the trial against Amanda and Rafaelle, and we can expect that the jury will demonstrate a fairly accurate understanding of the different testimonies from (a.o.) Dr.Stefanoni and Dr.Torre, and a fairly accurate understanding of DNA technology. Though, how the jury will make sense of the scientific facts in the actual circumstances (what it tells about who murdered Meredith) are not obvious.

Scientific references to the quoted papers are listed in my comment below.

Posted by Fiori on 07/11/09 at 07:30 AM in Evidence & witnessesDNA and luminolTrials 2008 & 2009Massei prosecution


To the Kerchers,

We as Seattleites and Americans offer our heartfelt apologies for the continuing offensive and classless behavior of the Knox/Mellas show.

At every turn they and their PR handlers have attempted to turn your tragedy into an OJ circus because it worked then.

Posted by jennifer on 07/12/09 at 02:15 AM | #

Ciao MfromBoston,

Thank you very much for your comments, and for the reference. I appreciate this, like I - as a foreigner in Italy (but not alienated) - also appreciate Pete’s invitation to post. People on this blog do a very good job and have provided many useful inputs to clarify the complex problems of the trial.

I rush with my references, not the least because it seems that we partly are drinking from the same pond:

-  Findlay, M (2008): “Juror comprehension and the hard case. Making forensic evidence simpler”, in: International Journal of Law, Crime and Justice 36 (2008), pp.15–53

-  Henderson, J.P (2002): “The use of DNA statistics in criminal trials”, in: Forensic Science International 128 (2002), pp.183–186.

-  Kaye, D.H., Hans, V.P., Dann, B. M., Farley, E. & Albertson, S (2007): “Statistics in the Jury Box: How Jurors Respond to Mitochondrial DNA Match Probabilities”, in: Journal of Empirical Legal Studies, Vol. 4-4, pp. 797–834, (December 2007)

Of cause I’ve benefited from much other material not quoted directly, but I will - in relation to your comment - like to mention: Jasanoff, S (1998): “The Eye of Everyman. Witnessing DNA in the Simpson Trial”, in: Social Studies of Science, Vol. 28, No.5/6 (Oct-Dec.1998), pp.713-740

Just to avoid misinterpretations; my field is not legal studies or comparative law, but in cultural studies of science and technology.


Posted by Fiori on 07/12/09 at 12:33 PM | #


Thanks for the heads-up. Unbelievable. Any tiny shred of sympathy I might have had for the Knox/Mellas clan is vanished. Sounds like little Miss Knox II may be in for a surprise come the fall.

“Biology undergraduate Deanne told the magazine: ‘At the end of this trial my sister Amanda will be coming home to Seattle with us. There are no other possibilities.’”

Clearly Miss Knox I isn’t the only one in that family who lives in her own reality and expects everyone else to live in it, too.

I think there’s great value in the fact that the jury in this case is not sequestered. They need to see this. It’s beyond disrespectful. The arrogance of it is only surpassed by its shameless stupidity.

Posted by wayra on 07/13/09 at 02:42 PM | #

Your comments about the studies on DNA evidence perception in the UK/US are quite interesting.

The Italian system, as you pointed out, differs significantly from the US mainly due to the composition of juries. Juries in the Italian system exist only in the Corte d’Assise and the Corte d’Assise D’Appello. As you all know, the Corte d’Assise is the Court in Italy that is responsible for trying serious crimes (generally crimes for which the Penal Code provides for a maximum prison term of 24 years or more) and it’s a mix jury of 6 lay persons (or ‘giudici popolari’ and 2 career judges (or ‘giudici togati’).

One thing to consider is that, although the intent of the ‘giudici togati’ is only to guide and counsel the ‘giudici popolari’, in reality the influence the ‘giudici togati’ they exert on the lay judges is quite significant. This reality is not necessarily liked by most Italian trial lawyers (especially when they know their client is guilty), as they consider it devoid of total impartiality. Add to that that Italian judges and prosecutors don’t have separate careers within the Magistrature and you realize why many trial lawyers often accuse the Italian system as being somewhat skewed in favor of the prosecution.

Said this, even if admittedly the Italian courts may be perceived as skewed in favor of the prosecutors, the system very rarely, if ever, produces instances where innocents have been sent to jail. Although it might be more difficult for the lawyer of a guilty defendant to sway professional judges with lots of experience, it is also true that the system overall is not particularly tough against criminals.

Therefore even in the event Amanda and Raffaele are found guilty don’t expect they’ll spend a lot of years in jail. In the corte d’assise d’appello sentences, even when confirmed, are ofter reduced and Italy has a system that grants a ‘semi-liberty regime’ to most convicts who behave (basically you go to jail only to sleep at night).

Not surprisingly, Italy has one of the lowest prison populations in Europe, in spite of the Red Brigades and Cosa Nostra. Not quite as low as the Republic of San Marino (currently with only one convict in their prison system), but very low nevertheless.

Posted by Commissario Montalbano on 07/13/09 at 07:40 PM | #

Hi MfromBoston. That made me smile! To me the Commissario seemed to imply that the system is perhaps slightly skewed toward the prosecution, not highly, and it is fair and careful and not prone to wrong convictions. 

Two things that we occasionally pick up on from our other legal watchers suggest that the system kinda balances out and may be easier on defendants than here in the US.

1) At least historically, apply enough political pressure and the system will cave in some instances, as there are considerable insecurities at the professional levels of the system.

2) The many judicial hearings prior to an actual trial are tough hurdles for the prosecution to have to keep jumping over. Any one of them could set a defendant free and they don’t have a parallel in the UK/US system.

This was the description of the process to trial from Nicki in Milan, which has won praise for accuracy and fairness in the emails and comments. It would be interesting to read you and the Commissario on it.

I agree with you and CM that a prison system that allows very early release is, well, not what we are used to here in the US.

The Italian prison system trains the perps in pizaa-making and barber-shop work, things like that, and there is TV in many of the cells. Some of AKs remarks from inside suggest that she finds it quite interesting at times. RS in contrast sounds disgusted at the lower-class elements to be found there.

We have had another commenter, also from Milan, telling us that this leniency of the prisons has been the result of a political thrust over the years and (she said) many in Italy feel it has gone too far.

If the defendants do go down, it may be a tough call for AK and her family to decide whether they should press for her to serve her time in a US prison. She may prefer to stay put. Possibly even marry RS and have conjugal visits, as is apparently legally quite possible.

Posted by Peter Quennell on 07/14/09 at 08:54 AM | #

Commissario Montalbano,

Many thanks for comments, they are highly appreciated. Im not an expert on the Italian legal system, but I find it very important to extend the discussion of DNA evidence beyond the formal representation of scientific evidence, and include the context of the Italian legal system.

My point was that, what ever the jury end up with as ‘truth’ depends upon the structure of the system (the organization of trial and pre-trials, the juror, the positions and recruitment of judges, etc), AS WELL AS the way credibility is created in the process. The latter is influenced by the content of a piece of evidence as well as the form (who is regarded as authorities by whom, on what subject, the rhetorical form negotiations, the order of presentation of evidence, etc).

Contrary to what we have learned in school, science is not objective; or put correctly: MAYBE science is objective, but mostly we DO NOT KNOW which part and under which circumstances it is so. Even experts, who are supposed to have gained privileged knowledge, do not agree. Here culture is significant.

We often seem to presume that we all read similar things out of – for example - visual presentation, i.e. that the rationale embedded in various visual illustrations, tables, schematics, etc. is universal. This is not so; this requires training in interpretation. To ‘make a match’ – to regard one thing similar to another – is a contested matter which poses profound philosophical, cultural, cognitive and psychological questions. Learning to interpret the signs, bips, lines, dots, from an instrument takes a long time and it requires experience from real life situations to earn competencies in identifying what is beyond ‘the signs of a machine’.

We are not present in the courtroom, so we do not see all the pieces of evidence in the context they are presented. Neither is we inside the heads of the members of the jury, so we do not know what they find is argued convincingly by the experts and what has not succeeded to convince. But we can analyse the processes and the patterns of authority which is in play in the case. And here knowledge on the organization of the legal system as well as how things work in practice, is very useful.

Reg. the discussion – and Pete’s points above - about the system leaning towards supporting the prosecution or not, the Italian system – as a system - is as conservative or liberal as any other legal system; a legal system is rarely the revolutionary avantguardia in any country.

Generally speaking, the US common law system is transformed by ruling of judges who changes precedence, while the civil law (Roman law) system is transformed by introduction of new laws (this is a major distinction, which in practice is less distinct, not the least because there is many variations of both systems). Judges in US system are assigned greater individual power to influence court, and the local differences are supposedly significant.

In this perspective the Italian system can seem conservative, meaning less open for changes induced by trials – and hence in favour of the prosecution, as the prosecution and judges together are taken to represents ‘the system’. But it is the working of the system that determines the outcome, and hence also the general notion of fairness or not. Generally Italians are as law abiding as any other European country and does not seem to find their system biased towards the prosecution. (Gibson and Caldeira: The legal cultures of Europe).

According to Carlo Guarnieri, an expert on legal cultures at the University of Bologna, the Italian legal system emphasizes rehabilitation over incarceration. The Italian system is very European and, in general terms, penalties are lenient. The general outlook of the court is in favour or rehabilitation, although today there is a lot of discussion that this doesn’t work satisfying. To mu knowledge, in Italy murder carries a minimum sentence of 21 years and a maximum of life. But life terms are rarely handed down, as you both have said, and acc. to Guarnieri, Italian practice reflects its Roman Catholic culture; that there embedded in the system is an attitude to forgive.

A few numbers – as you indicated yourself: The U.S. has the most prisoners per capita in the world, with 751 for every 100,000 people (The International Center for Prison Studies, London). Europe generally falls far behind: For example is Britain’s rate 151 per 100,000, Austria’s is 108 and Denmark’s is 66. (No mention of Italy in this article).

PS: Commissario Montalbano, do you appear on TV also in US?


Posted by Fiori on 07/14/09 at 11:36 AM | #

In reply to the above comments:

The Italian legal system emphasizes rehabilitation over punishment as this is what the Constitution requires at Article 27 [Rights of the Accused] paragraph (3). This is the art. 27 (all 4 paragraphs) translated:

(1) Criminal responsibility is personal.
(2) The defendant may not be considered guilty until the definitive sentence (i.e. after all degrees of appeal)
(3) Punishments may not consist in treatments contrary to humanity and must aim at the re-education of the convicted.
(4) The Death penalty is not permitted, except in cases provided by wartime military laws.

The number of convicts in Italy is the lowest in Europe after Denmark as a percentage of population. 67 every 100,000 people. When those figures came out last year there was an uproar in Italy, since there is no doubt that criminality in Italy is higher than in Scandinavian countries. One newspaper wrote in the headline: “We are the country where nobody ever goes to jail”.

Sentences in the Roman Law system do not establish precedent, including those by the Suprema Corte di Cassazione. However, sentences by the Sezioni Unite (United Sections) of the Suprema Corte di Cassazione have customarily been considered as ‘precedent setting’.

The Suprema Corte di Cassazione is divided into sections: Civil, Penal and Labor. Sometimes, important sentences that have wide repercussions are decided by all sections united. That is the only case when the decision has been accepted as a precedent setting.

The accusation that the Italian system is somewhat skewed toward the prosecution is a claim that trial lawyers make. Many magistrates and scholars disagree. And as mentioned above there are numerous safeguards to protect the defendant, even before the trial.

Berlusconi also thinks that prosecutors are favored in the Italian system, but you shouldn’t be surprised at his biases against Italian judges and magistrates, he’s a defendant in over a dozen cases relating to corruption, bribing, tax evasion and fraudolent accounting.

But last year his own party (which he founded in 1993 and filled with his companies’ executives and business associates) passed a law, known as lodo Alfano (from the name of the Justice minister) that guarantees immunity from all prosecutions to the four highest offices of the Republic (including his own office of Prime Minister), therefore all cases pending against him are suspended until he’s out of office (but I’m sure he wants to become President of the Republic next, another of the protected offices, to make sure that the immunity goes on until he dies).

Needless to say he truly loves the American system where the prosecution has no right of appeal in case of a not guilty sentence. Unfortunately for him, Italy doesn’t have the double jeopardy clause in its own constitution, and the Italian legal system is founded on the principle that the defense and the prosecution must have the EXACT same rights. It’s the so called principle of parity between the parties in the trial.

His attempt of a law passed in 2006 to curtail the right of the prosecution to appeal in the cases of ‘not guilty’ verdict, was struck down by the Constitutional court when it decided that such law would be unconstitutional as it would guarantee the defense a right (of appeal) which was not equally granted to the prosecution.

And finally, yes, I’m available in the US, but only on some PBS stations. Strictly in Italian, with English subtitles.

Posted by Commissario Montalbano on 07/14/09 at 02:46 PM | #

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