In your opinion, do legal proceedings and court decisions effectively utilize best available science?

It is a combination of many factors.  "Experts" often know their little fiefdom, but not how it interacts with other fields.  You generally have two extremes selected in cases, and thus miss the middle opinions and possible even the best data.  Judges' understanding of science is poor, as is many attorneys who use scientists.  Who is to say what is best?  "Peer Reviewed "Published (p =< 0.05) data, meta-analysis.  Is it reproducible? 

Doleman, Why most published meta-analysis findings are false, Controversies Colorectal Surg, 23, 925-928, 2019
Loannides, Why Most Published Research Findings Are False, Chance, 32, 1, 4-13, 2019
Begley, Drug development, raise standards for preclinical cancer research, Nature, 483, 531-533, 2012
Prinz, Believe it or not, how much can we rely on published data on potential drug targets, Nature Rev Drug Discov, 10, 712-713, 2011

Not always the court has availability to know how many information reqires and the pool of expert which can provide it

In my country people are all friends of political groups.  It is impossible to enforce a system of law that is 100% real.  There are and always will be favoritism in most cases

While the rigorous criteria of modern science seem a natural model for this evaluation, there are features unique to the courtroom that make the decision process scarcely recognizable by normal standards of scientific investigation. First, much science lies beyond the ken of those who must decide; outside “experts” must be called upon to advise. Second, questions of fact demand immediate resolution; decisions must be based on the science of the day. Third, in contrast to the generative adversarial process of scientific investigation, which yields successive approximations to the truth, the truth-seeking strategy of American courts is terminally adversarial, which risks fracturing knowledge along lines of discord. Wary of threats to credibility, courts have adopted formal rules for determining whether scientific testimony is trustworthy

Going for the 50/50 choice seemed for me as the best choice since this particular question is lacking from a context, specifically in regards to different scientific disciplines, and very importantly, with a special reference to geographical regions around the world. Legal issues, unfortunately, are not uniformly addressed around the world. I respectfully suggest this question to be reformulated.

50/50 is pretty ckear

Integrity is the fundamental factor in coming to fair decisions without bias or corruption. That is the basic professional aim of legal outcomes.

Forensic science gives the most objective analyses of evidences presented in a court of law, yet decisions are based on multiple factors, which can lead sometimes to an uneffective use of available science.

through written and oral consultation with well known experts in the field of interest

From personal experience in one formal proceeding and from intimate information about few others.

In most court proceedings, particularly in developing nations, judgements are based on technicalities rather than science. In situations where science could come in, it is never utilized probably owing to costs associated with such scientific investigation.

some time

Beaurucratic (Military and intelligence agencies official) interference and bribery are the main factors to affect courts decisions.

Generally, there is a goodwill to utilize science results, but 
 a) best science is not always leading directly to the unambiguous conclusions

b) conclusions should be communicated by the way that non-expert in the respective scientific discipline (e.g. judge) will understand it clearly

c) sometimes, good rhetoric prevails the “dry” scientific data

Because the court depends on the expert opinions as shared with them by the identified experts. The unbiased opinions of these experts is very important because the experts so chosen are from a few institutions/ governmental officials and hence is not always totally fair on the scientific facts and is adulterated by many other forces, too.

This is my both, the best and most important expertise, and unfortunately not used in legal proceedings and court decisions, because it was not legal proceedings and court decisions in COVID 19 pandemic: Radosavljević V. Analysis of COVID-19 outbreak origin in China in 2019 using differentiation method for unusual epidemiological events. Open Medicine 2021; 16: 955–963.

The most updated state of art needs an aknowledge level that is hard to reach out "on time" out of the science rooms. it is difficult to translate the multilevel and multidiscipline approach to legal proceedings and be clear enough to be understood and used in court decision

The legal situation is us versus them, so the science of probably somewhere in between, the usual situation, is not an option if trying to win a case. Therefore, extreme "expert" views are the norm in legal situations unless the cross-examiner can pick out the flaws in the arguments presented - a difficult job for a lawyer.

The myriad Roundup herbicide product lawsuits is a good example of ignoring published science and relying on a flawed interpretation by IARC that labeled glyphosate active ingredient a probable human carcinogen, solely based on high dose injections into animals (the agency even admitted the human epidemiological evidence was very weak).  My understanding is the court was not open to alternative opinions plus the case rested on purloined Monsanto emails (some lawyer forgot to tell the principals don't write emails because they are all discoverable in court proceedings).  Thus, based on the Roundup lawsuits with its bevy of ambulance chasing lawyers, I would say that court proceedings can go off the rail and not allow the best available scientific opinions or conclusions.  However, I rated the issue 50/50 because there are cases where scientific information seems to be the major factor in the lawsuit outcomes.

Public functionaries are contaminated by political ideologies.

Real clinical life differs from positions stated by counselors of the court, since frequently they are not practitioners of the discipline involved in the judgement.

They normally don't have all the scientific evidence available.

In my field (psychology), misunderstandings of scientific literature are frequent, considering the multiple theoretical perspectives characterising the discipline. 

not every part of Africa has developed to that level and so it depends

This refers to my experience in Italy: the Judges usually nominate their own consultant(s) who usually interact with the plaintiff's, prosecutor's and defendant's consultant. The nomination is frequently not based on an objective evaluation the CV  but on personal knowledge or "political" affinity. 
In addition, media misunderstanding on science is also carried into Court and, not rarely, plays a major role

The court selected experts generally don't have a background in Omics technology. They are behind.

Especially in a developing countries, the decision are dominated by political will and affiliations. Also influenced by political powers.

In about half the cases I've worked on, juries and/or judges don't understand the science.  This might be because it wasn't explained adequately or they just didn't have the educational background to understand more complex ideas.  What is more like to sway the jury or judge is how sure an expert seems about their opinion and how the expert "connects" with the triers of fact.  The saying "often wrong, but never in doubt" comes to mind...

They seem to rely on perception and, like most media, etc. focus only on hazard.  They seem to never look at the known/potential health risk (hazard x exposure) - that should be what is looked at/evaluated/reported.

Unfortunately, legal proceedings and court decisions rely on persuasiveness of arguments (rhetoric being more important than fact), precident and construction of the controlling legislation.  Science may have provided factual bases at the time a law, regulation, or policy was formulated, but the legal system tends to use that as the touchstone and disregards more relevant factual information.

Court too influenced by politics 

I find that, with respect to depositions and trials,  plaintiff expert often rely on distortions, biased scientific analysis and, less frequently, od hominem attacks on the opposing side's experts.  It's not as problematic with respect to judicial decisions.  Still, I remain mystified by how frequently judges allow huge awards in glyphosate cancer cases.

Lay jury rarely have sufficient understanding of science and the statistical unalysis necessary to understand the conclusion. Thus defence and prosecution cherry pick "experts" to support their point of view without regard to the quality of science.

Too much lobbing in many cases, in many cases the judges do not understand the details of importance of certain proofs which support accepting or declining the final decision. In many cases also scientists have different attitude to a particular decision, most of them because they have doubts to some proofs, but some of them also because of lobbing, sometimes with unfair background.

Questions are asked by the attorneys, not by expert witnesses. Cases are determined on the basis of narratives (accounts, theories), which scientific evidence is mobilized to support or undermine.
It is primarily jousting between lawyers. Science is not a primary consideration or an end in itself. Effectiveness is determined mostly by legal factors (e.g., lawyer's skill and reputation). 

As an engineer/scientist for 44 years, I routinely see scientists not using the best available science. How could you expect lawyers and judges to then?

Often there is no one on either side, or on the bench, who has the background and knowledge to recognize krappy science or mis-interpretation of valid research or cherry-picking of data by an "expert".

It will depend first of the proofs that will be allowed in court, and then would be the type of science that can be understandable for the jury.

In most of the time sicentific evidences used for deceion making in developed countries. However, developing coutries not used because the evidences generated from scientific investigation were limited. 

  No,they seem to often use junk science, and/or misrepresent statistics.

It depends very much on the case, setting, jury, and judge and lawyers involved.

Politics often obscure the facts

One side can always find shoddy science to make a point. 

I think it depends on the chemical and the court.  The atrazine and talc cases don't seem to rely on the best science.

The best available science is not always the best science (publication bias, vested interests)
Courts do not tend to have the expertise to understand e.g., statistical arguments about variability
The legal process is adverserial, not proceeding by doubt.

Depends on the science - the process of science is fraught with missteps and self-correction. So, the veneer of "scientific certainty" can be mishandled by either side.  

An example is the carcinogenicity claims aboout glyphosate, the IARC review and the CA Prop 65 warning requirements.  Sometimes, regulators also ignore relevant data in the ecological and endangered species act evaluations.  There are examples for many active ingredients.

A typical example is the court decisions on the cancer risk related to the use of glyphosate-containing herbicides. Scientific evidnce showing that the active compound is not carciongenic is just ignored.

Access to scientific literature may be difficult or ignored by the non-scientist third parts.

Scientific evidence-based judgment would be utilized whenever there is uncertainty in making decisions. 

The current information is not always available.

I don't know that they use science, but they do use expert witnesses who can be skillful in the use of evidence to support a particular viewpoint without necessarily using the "best evidence" by view of the quality of the evidence itself. 

I am an expert witness in the high court in Bloemfontein and they use me as I am an accredited scientist in a tertiary education; with a PhD with a high h rating  as well as having experience with lecturing jurisprudence for veterinary students in regard to  animal welfare. 

My personal experience is that whenever I submit my written expert testimony telling a convincing story backed by the science that is simple enough for the jurors to understand, attorney of the opposite party try their best to throw my testimony using lame arguments, like I don't have enough expert witness experience, etc. They try to do the same to my depositions, very frustrating. When they cannot dispute the scientific facts, they try to throw the whole report and/or deposition.

Depends on the case. The current U.S. Supreme Court case on mifepristone is being argued by religious zealots posing as physicians, giving a bad name to the entire profession. 

In many scenarios it is due to lack of scientific facility.

Often, a clearly problematic issue that has a scientific basis will be settled in court due to a legal loop hole where the entity filing the suit is determined not to have standing on the issue. The case will be thrown out but the underlying scientifically-based issue remains.

Sometimes the scientific evidence is ignored.

There were two talks at the Society of Toxicology this year from speakers who frequently communicate research in criminal or civil trials.  I believe that in most cases, experts utilize the best available science.

This is based on my experience as an expert witness in two legal proceedings.  I was invited to produce a report and undergo deposition.  I'm a behavioral epidemiologist and am familiar with building causal arguments and understanding the strengths/weaknesses/bias of epidemiological study designs.  My literature review and interpretation were key pieces of evidence that led to several verdicts.  The opposing lawyers presented medical expert opinions which are valid, but in my experience medical opinions do not stand in comparison to a careful epidemiologic causal review of evidence. 

To answer the question - I have participated in and have seen the best available scientific evidence win court proceedings.  I have also witnessed methodologically sloppy opinions that are not persuasive.  

There is a fundamental difference between the legal and the scientific definitions of causality. The level of evidence required by court to declare relationships is minimal and the term probability (especially the attempt to estimate the proportion contribution of different risk factors) is used superficially and in practice, wrongly.

There is cherry picking of what science is used. 

While experts may be used in legal proceedings, if a jury or judge does not understand science/math/statistics then the outcome is not necessarily based on the best science.  

The court room decision are made without interaction with science experts for deep understanding of scientific background of modern day issue. 

Not enough. However, I think that science is used to a relatively greater extent in the criminal field.

I think there is often a temptation to highlight the science that is most favorable to one’s legal position, instead of critically evaluating the whole body of evidence on a certain topic.

Especially when it comes to genetic analysis, there is a lack of competence relating to probabilities in both lawyers and judges, with potential serious prejudice to the outcome of the trial

There are cases where the data is not sufficient.

This is so because in most cases courts may be in a hurry to conclude cases and one party may not have the resources to utilise all options including all scientific information available or obtainable. 

If competent consultants are engaged, the evidence should be understandable by the judge and the jury.

Based upon my experience as a consultant and expert witness on issues pertaining to health effects of environmental exposures (mostly endocrine related) court decisions at times do not take into consideration all of the scientific information available.

There are often large disparities between the quality of science used to influence and reach decisions in litigation, and conflicting expert testimonies on science matters are generally confusing to non-technical juries resulting in emotion-based decision-making vs that based on an actual assessment of what is the best science.   
Further contributing to confusion, judges generally defer to allowing a wide range of science opinion in the courtroom.

 Many courts have been politicized.  Some judges use their moral beliefs in preference over the science.  Due to the expert witness process, the best science may not be presented since the experts, though supposedly independent, may choose to present biased information, due to financial or moral influences 

The courts use the law or constitution and not science

Seldom do the courts take into account the best science or the most scientific arguments. 

Unfortunately, ai least in my country, there is not really a high control on whom is colled to be the expert on scientific matters. 

This depends of the quality of the legal representation on both sides.