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Scientific evidence

 
Law Encyclopedia: Scientific Evidence
 
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This entry contains information applicable to United States law only.

Evidence presented in court that is produced from scientific tests or studies.

Scientific evidence is evidence culled from a scientific procedure that helps the trier of fact understand evidence or determine facts at issue in a judicial proceeding. Under rule 702 of the Federal Rules of Evidence and similar state court rules of evidence, "a witness qualified as an expert by knowledge, skill, experience, training, or education" may testify and offer opinions in court if "scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue." Article VII of the Federal Rules of Evidence contains other rules on expert testimony and scientific evidence. All states have rules on expert testimony and scientific evidence that are similar to the rules in article VII.

Expert testimony on scientific evidence is different from ordinary testimony from laypersons. A lay witness may testify to inferences and give opinions only if they are rationally based upon her perceptions of the subject of the testimony. Experts, by contrast, may give opinions and testify about possible inferences based in part on information obtained from secondhand sources and not from observation of the object of the testimony. For example, a layperson would not be allowed to take the witness stand and offer an opinion on a plaintiff's injury unless he had witnessed relevant information regarding the injury. However, a doctor who is certified as a specialist in the particular injury could take the stand and offer opinions on the injury based not only on an examination of the plaintiff but also on secondhand information that is normally relied on by experts in that particular field of medical study.

One of the most important issues that arises in expert testimony is which scientific procedures a court should accept as evidence. Many scientific procedures are not seriously in dispute and are accepted by courts with little or no inquisition into their validity. Examples include fingerprint tests for purposes of identification, blood tests, breathalyzer tests for alcohol consumption, and ballistics tests of bullets and their impact areas. These scientific procedures are so widely accepted that a court may take judicial notice of the procedure's validity. Judicial notice means that the parties in the case do not have to present evidence to the court to establish the validity of the scientific procedure. In some instances legislatures have specifically authorized the use of scientific tests, such as breathalyzer tests for suspected drunk drivers.

Whether they are judicially noticed or legislatively mandated, scientific tests that are universally accepted must be presented by a qualified expert. A person is established as a qualified expert before the court through questioning by the attorney who is using the witness as an expert. The attorney asks a series of questions to establish that the witness has adequate education and training to testify as an expert — a process called laying a foundation for the witness. Once the court is convinced that the witness is an expert on the procedure or subject matter that will be presented as evidence, the witness gives an expert opinion to the exact procedures that were used or the factual circumstances that arose in the case at hand. For example, assume that a person sues a doctor for medical malpractice, arguing that the defendant failed to set a broken bone properly. If the plaintiff offers a bone specialist as an expert witness on the issues surrounding the care he received from the defendant, the expert witness must testify to her credentials and give details about the plaintiff's treatment.

Some scientific tests and examinations that are not universally accepted are nevertheless generally considered reliable. Some examples include neutron activation analysis to determine the identity of goods, voiceprints to determine a person's identity, and genetic testing, or DNA analysis. These types of scientific procedures may be accepted in the medical communities, but they are not so established that they may be judicially noticed as automatically valid sources of scientific evidence. They may be admitted as evidence, but only after an expert witness has testified to the validity of the test. In determining whether to admit scientific evidence from procedures that are not universally accepted, a court must ask whether the test is reliable. A technique's reliability depends on a number of factors, including whether the technique can be or has been tested, whether it has been subjected to peer review, whether the test procedures have been published, whether the test has a margin of error and, if so, at what rate, and whether the technique, as applied, conformed to existing standards for the test (Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125 L. Ed. 2d 469 [1993]).

In some instances courts are reluctant to admit certain scientific evidence because the procedures yield results that are not considered sufficiently reliable to be used as evidence. Such procedures include polygraph and chemical tests that have been created to determine whether a person is telling the truth. If all parties agree that testimony derived from such procedures shall be admissible, however, a court is free to allow the evidence to be introduced.

In any case, regardless of the level of acceptance of a particular scientific procedure, the scientific evidence presented must be relevant to the issue at hand. Furthermore, the scientific evidence must have been obtained in a manner that is consistent with the way such evidence is normally obtained. For instance, assume that a physicist intends to testify to the speed of the defendant's vehicle in a personal injury case stemming from a car accident. If the physicist used different methods from those used by other physicists in determining a vehicle's speed, the court may refuse to allow the physicist to testify as to the vehicle's speed.

An expert witness giving testimony on scientific evidence may offer opinions on issues related to that evidence. An expert witness may also give an opinion on the ultimate issue in the case. Under rule 704 of the Federal Rules of Evidence, however, an expert witness testifying with respect to the mental state or condition of a criminal defendant may not state "an opinion or inference as to whether the defendant did or did not have the mental state or condition constituting an element of the crime charged or of a defense thereto." This rule, which is applied by courts only in criminal cases, was approved by the U.S. Congress in 1984, largely in response to the outcome of the criminal prosecution of John Hinckley, who attempted to assassinate President Ronald Reagan in 1981. Hinckley was charged with attempted assassination, assault on a federal officer, and use of a firearm in the commission of a federal offense, but was found not guilty by reason of insanity after the jury heard testimony from a psychiatrist who declared that Hinckley could not be found guilty because he lacked the knowing mental state required for a conviction on the charges.

The weight given to scientific evidence may vary according to the particular test that yielded the evidence. One party's expert testimony may be convincing, but it may not be dispositive of the case because the other party may have experts from the same field who have studied the same evidence and come to different conclusions. Experts have become indispensable to the vast majority of litigated cases, and many cases, civil and criminal alike, come down to a battle between experts. One notable exception to this trend is the paternity case, where blood test results or DNA test results can establish the ultimate issue in the case. This is true, however, only if the parties in the paternity case agree that the particular tests will be conclusive and if the tests show that the individual named as the father could not be a parent of the child in question. If the tests show that the indivi- dual named as the father could be the parent, the test results will not dispose of the case, and the parties will have to present further evidence.

Courts have the discretion to appoint an expert witness to testify to scientific evidence. Under rule 706 of the Federal Rules of Evidence and similar state court rules of evidence, a court may appoint an expert to present evidence on a particular topic and order compensation for the expert's time and effort. Typically, in a civil case, the parties must apportion the costs as the court directs. In just compensation cases under the Fifth Amendment and in criminal cases, the court orders payment for the expert out of government funds.

See: DNA Evidence; Fingerprints; Forensic Science; Insanity Defense; Paternity Suit.

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Wikipedia: Scientific evidence
 
Home > Library > Miscellaneous > Wikipedia
This article is about the concept of scientific evidence in pure science. For the legal term, see Scientific evidence (law).

Scientific evidence is evidence which serves to either support or counter a scientific theory or hypothesis[citation needed]. Such evidence is expected to be empirical and properly documented in accordance with scientific method such as is applicable to the particular field of inquiry[citation needed]. Standards for evidence may vary according to whether the field of inquiry is among the natural sciences or social sciences[citation needed].

Contents

Principles of inference

Evidence is information, such as facts, coupled with principles of inference (the act or process of deriving a conclusion), that make information relevant to the support or disproof of a hypothesis[citation needed]. Scientific evidence is evidence where the dependence of the evidence on principles of inference is not conceded, enabling others to examine the background beliefs or assumptions employed to determine if facts are relevant to the support of or falsification of a hypothesis[1].

A person’s assumptions or beliefs about the relationship between alleged facts and a hypothesis will determine if that person takes the facts as evidence[1]. Consider, for example alternative uses of the observation that day and night alternate at a steady rate. In an environment where the observer makes a causal connection between exposure to the sun and day, the observer may take the observation of day and night as evidence for a theory of cosmology. Without an assumption or belief that a causal connection exists between exposure to the sun and the observance of day, the observation of day will be discounted as evidence of a cosmological theory.

A person’s assumptions or beliefs about the relationship between alleged facts and a hypothesis will also determine how a person utilizes the facts as evidence. Continuing with the same example, in an environment where geocentric cosmology is prevalent, the observation of day and night may be taken as evidence that the sun moves about the earth. Alternatively, in an environment where heliocentric cosmology is prevalent, the same observation may be taken as evidence that the earth is spinning about an axis[1]. In summary, beliefs or assumptions about causal relationships are utilized to determine whether facts are evidence of a hypothesis.

Background beliefs differ. As a result, where observers operate under different paradigms, rational observers may find different meaning in scientific evidence from the same event[2]. For example, Priestly, working with phlogiston theory, took his observations about the decomposition of what we know today as mercuric oxide as evidence of the phlogiston. In contrast, Lavoisier, developing the theory of elements, took the same facts as evidence for oxygen[3]. Note that a causal relationship between the facts and hypothesis does not exist to cause the facts to be taken as evidence[1], but rather the causal relationship is provided by the person seeking to establish facts as evidence.

A more formal method to characterize the effect of background beliefs is Bayesianism[4]. Bayesian theory provides that one’s beliefs depend on evidence to which one is exposed and one’s prior experiences (probability distribution, in Bayesian terms)[5]. As a result, two observers of the same event will rationally arrive at different evidence, given the same facts, because their priors (previous experiences) differ.

The importance of background beliefs in the determination of what facts are evidence can also be illustrated using syllogistic logic as provided by Aristotle. A standard syllogism is a triad where two propositions jointly imply the conclusion[6]:

All men are mortal,
Aristotle is a man; therefore Aristotle is mortal.

If a person does not believe the propositions are affirmative, the facts will not be accorded the status of evidence.

Utility of Scientific Evidence

Philosophers, such as Karl R. Popper, have provided influential theories of the scientific method within which scientific evidence plays a central role[7]. In summary, Popper provides that a scientist creatively develops a theory which may be falsified by testing the theory against evidence or known facts. Popper’s theory presents an asymmetry in that evidence can prove a theory wrong, by establishing facts that are inconsistent with the theory. In contrast, evidence cannot prove a theory correct because other evidence, yet to be discovered, may exist that is inconsistent with the theory[8]. See falsificationism for more on this view of scientific evidence.

Philosophic versus Scientific Views of Scientific Evidence

The Philosophic community has invested extensive resources to address logical requirements for scientific evidence by examination of the relationship between evidence and hypotheses, in contrast to scientific approaches which focus on the candidate facts and their context[9]. Bechtel, as an example of a scientific approach, provides factors (clarity of the data, replication by others, consistency with results arrived at by alternative methods and consistency with plausible theories) useful for determination if facts rise to the level of scientific evidence[10].

A variety of philosophical approaches are available for the evaluation of evidence, many of which focus on the relationship between the evidence and the hypothesis, to determine if the facts rise to the level of evidence. Carnap recommends distinguishing such theories of evidence using three concepts: whether the theory is classificatory (does the evidence confirm the hypothesis), comparative (does the evidence support a first hypothesis more than an alternative hypothesis) or quantitative (the degree to which the evidence supports a hypothesis)[11]. Achinstein provides a concise presentation by prominent philosophers on evidence, including Carl Hempel (Confirmation), Nelson Goodman (of grue fame), R. B. Braithwaite, Norwood Russell Hanson, Wesley C. Salmon, Clark Glymour and Rudolf Carnap[12]

Based on the philosophical assumption of the Strong Church-Turing Universe Thesis, a mathematical criterion for evaluation of evidence has been proven, with the criterion having a resemblance to the idea of Occam's Razor that the simplest comprehensive description of the evidence is most likely correct. It states formally, "The ideal principle states that the prior probability associated with the hypothesis should be given by the algorithmic universal probability, and the sum of the log universal probability of the model plus the log of the probability of the data given the model should be minimized." [13]

See also

References

  1. ^ a b c d Longino, Helen (March 1979). Philosophy of Science , Vol. 46. pp. 37–42. 
  2. ^ Thomas S. Kuhn, The Structure of Scientific Revolution (1962).
  3. ^ Thomas S. Kuhn, The Structure of Scientific Revolution, 2nd Ed. (1970).
  4. ^ William Talbott "Bayesian Epistemology" Accessed May 13, 2007.
  5. ^ Thomas Kelly "Evidence". Accessed May 13, 2007.
  6. ^ George Kenneth Stone, "Evidence in Science"(1966)
  7. ^ Karl R. Popper,"The Logic of Scientific Discovery" (1959).
  8. ^ Reference Manual on Scientific Evidence, 2nd Ed. (2000), p. 71. Accessed May 13, 2007.
  9. ^ Deborah G. Mayo, Philosophy of Science, Vol. 67, Supplement. Proceedings of the 1998 Biennial Meetings of the Philosophy of Science Association. Part II: Symposia Papers. (Sep., 2000), pp. S194.
  10. ^ William Bechtel, Scientific Evidence: Creating and Evaluating Experimental Instruments and Research Techniques, PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association, Vol. 1 (1990) p. 561.
  11. ^ Rudolf Carnap, Logical Foundations of Probability (1962) p. 462.
  12. ^ Peter Achinstein (Ed.) "The Concept of Evidence" (1983).
  13. ^ Paul M. B. Vitányi and Ming Li; "Minimum Description Length Induction, Bayesianism and Kolmogorov Complexity".

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

 
 

 

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Law Encyclopedia. West's Encyclopedia of American Law. Copyright © 1998 by The Gale Group, Inc. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Scientific evidence".  Read more

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