You're gonna be under arrest. Excuse me, sir, I need you to put your hands on the car.

On television, police programs about investigating a crime are fast paced, and usually get resolved in one episode. But real life situations may be treated quite differently, are more meticulous, and can take substantially longer. Officers must find evidence that a crime has been committed and present that evidence to a prosecutor.

The prosecutor in turn must get the evidence admitted into court, and a jury or judge must evaluate the evidence to determine a defendant's guilt. This is the story of the American criminal justice system.

What is evidence? We use it every day. When we get up in the morning, we look outside to see if it's sunny, and check a thermometer for the temperature. We use this evidence to decide what to wear. When we disagree with someone, we use evidence to prove our point. Evidence is anything that is used to prove or disapprove a fact.

Evidence can be physical evidence, it can be direct evidence, it can be circumstantial evidence, it can be physical evidence. But it's the information that's presented in court to the judge or jury to be able to determine in a criminal case, guilt or innocence.

Police use evidence to solve crimes. When they believe a crime has been committed, the search for evidence begins. Evidence may include documents and other physical objects.

Looked like he had a TV in his arm.

It even includes eyewitness accounts of what occurred.

Officers get on the scene, they begin to gather evidence. They look around the perimeter, and then they work their way in, usually trying to find out what's occurred, how they know something has occurred, and looking for pieces of evidence. Something that will clue them in to how something happened.

And also begin questioning witnesses. Initially, everybody's probably going to be questioned, as we determine how someone knew the people involved, or what they witnessed.

No matter how stealthy or careful they think they might have been, criminals always leave behind some sort of evidence for investigators to collect and use to find out who committed the crime, and bring them to justice.

When a crime is committed, the place where it was committed is often cordoned off in order for detectives and investigators to evaluate the scene and collect evidence. Items or findings from a crime scene are criminal evidence. They're used to establish that a crime has been committed and identify blame or fault.

The prosecution and the defense will make use of criminal evidence to convince the judge or the jury that its version of the facts is true. That's called the burden of proof.

What constitutes acceptable criminal evidence varies somewhat between legal systems, although ideally, evidence provides reasonably reliable information that gives a more complete picture of a crime.

Depending on the type of crime, different evidence will be sought. If it was something violent, like a shooting or a stabbing, we're looking for a weapon that was involved, or evidence that would help direct us to where the weapon would be found. How we would be able to establish ownership of the weapon, or who possessed the weapon before the crime.

In property crimes, we're looking often for fingerprints, or for damaged property. Something that will, again, clue is in to who committed the crime and where they've gone. What happened to the stolen items, how they were taken, and who was present at the time the crime occurred.

Hollywood has glorified crime scene investigation, or CSI. We've all seen examples of chaotic evidence collection and oddball detectives solving the crime on the spot. How accurate are they?

Some shows have detail as it relates to solving the crime. They have the appropriate equipment, and so forth. But remember, a crime has to be solved within 40 minutes, and in that context, we have a situation where testing that may take a day, or two days in real life is completed within 10 minutes or less.

So the reality is the equipment is appropriate, some of the terminology is appropriate, but it's the time that this all takes place. And it takes a lot of diligent effort on individuals' part.

Whether they be a detective in the field, at the crime scene itself, or whether it be an analyst in the laboratory. These individuals may take hours or days to analyze evidence, not minutes.

CSI is a methodical documentation of the conditions of the scene and the collection of any physical evidence that tells what happened, and points to who did it.

Evidence is ordinarily obtained by the investigating officers when in a criminal case, when the investigating officers would go to a crime scene, they would typically interview and take statements of witnesses. Interview, take statements of the victim.

Collect the physical evidence that, for example, if it's a case involving an assault or a battery, or a robbery by force with the use of a baseball bat. And the baseball bat broken and bloody, left at the crime scene. The police would take that into evidence, and the evidence could be introduced to trial against the defendant.

Collecting and documenting evidence is only part of what crime scene investigators are trying to accomplish. The ultimate goal is to convict the person who committed the crime. So while sealing one or two hairs in a plastic bag, the investigator is also following protocol for the preservation of every piece of evidence.

That helps the crime lab to make the best use of it in reconstructing the crime or identifying the criminal. CSI also has to be sure that the collection and documentation of evidence observe all rules for admissibility in court.

In order to ensure fairness, in order to allow both sides to prepare, both sides are supposed to engage in what's ordinarily called pretrial discovery. And what's called pretrial discovery is generally there's just an exchange of information about each other's cases.

So ordinarily, each side will have to share with the other side the list of witnesses that they expect to call, the physical evidence that they anticipate introducing. Any expert witnesses that they plan to call to testify.

CSI is not a one man operation. A team of experts will be called in when a crime has been committed. Police usually arrive first to secure the scene and make sure no evidence is destroyed or tampered with. Crime scene investigators are in charge of documenting and collecting evidence.

Sometimes the district attorney is called to the scene to help investigators obtain search warrants. If it's a homicide, the medical examiner might offer a preliminary cause of death at the scene.

There was a van come up, and we noticed it.

Detectives interview witnesses and consult with the CSI unit. Lab results of evidence will be sent to the lead detective on the case.

Police officers are fact gatherers, essentially. We gather the information, we question people, we collect evidence, and we pass along the body of that to the prosecuting attorney, who will then take the matter to court and argue the case before a judge. So it's a hand in hand relationship.

Although we have different tasks, the goals is the same, and that is to prosecute successfully those who have committed crimes.

Almost anything can be considered evidence, but whether a court gets to consider a piece of evidence during a trial depends on a set of rules. The rules or laws of evidence are drafted by the courts to govern how evidence is admitted, and how civil and criminal trials proceed.

Many states have adopted or modelled parts of their evidence laws after the federal rules of evidence. These rules govern the admission of facts in the US federal court system, and determine how the parties involved may prove their cases.

What the rules of evidence are designed to do is keep out, assure that only relevant evidence is introduced, and keep out irrelevant evidence. That's exactly what their principal function is, and there are a lot of different rules that deal with different aspects of the trial.

Laws of evidence vary from state to state, but some rules are almost always observed. Probably the most important rule is the requirement that all evidence be relevant to proving or disproving a fact in the case before the court. If evidence is deemed not relevant, it's inadmissible.

Evidence is allowed into the proceeding by a judge if the side presenting the evidence can present some testimony to give some assurance that that evidence is really what it appears to be.

For example, the chain of custody could be important because if it's an items seized from a crime scene that has, for example, a fingerprint on it.

It would matter that in fact that didn't get inadvertently or accidentally switched, mixed up in the evidence locker with evidence from another offense from a different location, or maybe it's just the sample print taken for comparison purposes of that accidentally mixed up with the sample from the crime scene.

It would create the illusion of guilt when in fact it wouldn't be evidence of guilt of all. So in order for evidence to be introduced to trial, it has to be, the term is usually authenticated. There has to be some testimony that it's in fact what it appears to be.

Many think a person's prior misdeeds or criminal record will automatically be admissible. Not so. The rules take into account that this background may have a prejudicial effect, and could help convict a defendant wrongly. Inclusion of character evidence is severely limited in most cases.

Hearsay is testimony made in court about a statement made by a person other than the one testifying. However, the rules do vary in different jurisdictions. But prior statements are usually admissible. That's one of the reasons a person's Miranda Rights are so important when questioning a suspect in a crime.

If the police fail to give a Miranda Warning before questioning a person in custody, the evidence gathered from the interview cannot be used against the person. Evidence becomes prejudicial when it sparks an improper decision regarding guilt. A decision based more on emotion rather than rational thinking.

For example, a confession that is alleged to have been made in a lawful manner. So you have to look at that and consider whether or not all of the constitutional rights that are required to be followed have actually been given. So I'm always looking at what the law says is allowed, and what I believe is proper based on what's been presented to me.

Confessions are considered top shelf evidence in police investigations, but are also a source of controversy. If a confession is voluntary and the suspect is of sound mind, it may be admissible. If it's involuntary, and the defendant's lawyer maintains that it was obtained through coercion, duress, or trickery, then it may be deemed inadmissible.

Then there's the false confession. If a court suspect's a confession is fabricated or produced because of the stress of the interrogation, then additional corroborating evidence may be required before an individual may be convicted on a confession alone.

Some evidence tells a story in and of itself, the proverbial smoking gun in a suspect's hand, for example. Other types of evidence may not be immediately identifiable as evidence of guilt or innocence.

But for every bit of evidence that's offered by legal teams, there's a rule governing its use, and a judge that will rule on its admissibility, if there is not a clear cut law that applies.

What goes on at the crime scene? Collecting and documenting evidence is called crime scene investigation. But what goes on in the crime lab is called forensic science.

Forensic science is the process by which you take scientific principles, scientific concepts, and you apply those to determining the source of evidence, the composition of evidence, and try to link that evidence to a particular individual who might be a suspect, or actually take that evidence and determine that an individual is not guilty of a particular crime.

Just as there are many types of evidence, there are many different types of forensics. Ballistics specialists identify and analyze firearms and the flight path of bullets. These experts can immediately tell the variations in bullets fired from different guns by analyzing the unique markings etched into the bullet as it's fired.

Forensic pathologists are medical examiners who perform autopsies, and can usually determine the cause and approximate time of death. Identifying human remains to determine a person's age, height, weight, gender and cause of death is forensic anthropology.

There are also forensic specialists who deal exclusively with blood spatters, dentistry, handwriting, disease, and toxicology. There's also a well populated field of computer forensics technicians who know that pressing the delete key does not delete evidence of crime.

It's always there, and waiting to be discovered. Something else that never goes away or changes is a person's fingerprints.

The use of fingerprints is probably the most popular form of biometric in the country today. There's advantages to fingerprints in that they can be left at crime scenes. They're called latent fingerprints. So if a suspect was to touch something at a crime scene where we're able to lift that fingerprint, it can be used for identification purposes.

The FBI maintains the integrated automated fingerprint identification system, or IAFIS, which is a fingerprint and criminal history databank accessible to state, local, and federal law enforcement officials 24/7. Prints, criminal histories, mug shots, scars, photos of tattoos, plus physical characteristics such as height, weight, hair and eye color.

Even aliases are available for more than 70 million suspects in the IAFIS master file, along with more than 30 million civil prints.

When I started with the Boston police department approximately 29 years ago, it could take upwards to six months to get a response back from the FBI.

So if you arrested somebody for a relatively minor charge, that person was eligible for bail. Unfortunately, if they're wanted for a very serious charge in another state and gave us an alias, a false name, that person could walk out of that police facility, and then just run.

The advantage to electronic fingerprints that I've seen is that we change the booking process. So now we hold the prisoner until the response comes back from the FBI. Everybody in this country is entitled to the presumption that they're innocent until proven guilty, so the person's eligible for bail in most circumstances.

But the advantage of electronic fingerprinting is we get the response back in a very short period of time. In my experience from Boston, it usually was 15 minutes. And I remember one time in my career, very early on we saw the advantages to it.

We arrested on individual for a very minor crime, and the response came back that he was wanted in North Carolina for a murder. And that's the advantage. You have the prisoner at the booking facility. You can make the identification, and you can do a national check.

Fingerprints used to be the gold standard in crime detection, but more often than not, they're now playing second fiddle to deoxyribonucleic acid, or DNA. DNA can be used to identify criminals with incredible accuracy when biological evidence exists. Even when a criminal is wearing gloves.

DNA is, of course, present in most all of our cells. There are certain cells that as they mature, they lose certain types of DNA. But for the most part, every cell within our body, we have the same DNA that we inherited from our mom and from our dad. So we can use that DNA to identify an individual.

And so what we would like to do is obtain the sample from the crime scene. Again, maintain the chain of custody with that sample. And then when we get it to the laboratory, we remove the DNA from the host cell in which it resides. Then we take and purify the DNA and analyze it.

We use very sophisticated equipment to do this analysis, but at the end of the process, we determine a DNA profile. The DNA profile borders on being unique.

We use statistics that the chance of a random individual having that very same DNA profile is one in quadrillions, or one in trillions. So it's a very unique identifier for this type of evidence.

When DNA a is found at the scene or is taken from a suspect, it can be submitted for identification to CODIS, the combined DNA index system, a national, state, and local set of databases for the storage and exchange of DNA profiles.

More and more, DNA samples are being taken from suspects and crime seems to be recorded and stored to help solve and find all types of crimes and criminals. DNA like fingerprints, is unique to every person, even identical twins. DNA is is generally used to solve crimes in one of two ways.

In cases where a suspect is identified, a sample of that person's DNA can be compared to evidence from the crime scene. That may establish that the suspect committed the crime. If a suspect hasn't been identified, biological evidence from the crime scene can be analyzed and compared to offender profiles in DNA databases to help identify the criminal.

No matter how careful the criminal is, there will always be some sort of evidence left at the scene of the crime, and it's up to law enforcement to find it and use it to prove who the criminal is.

A murder weapon. Photographs. Phone records.

Well, I noticed that--

Or the testimony of someone who saw exactly what happened. There are all sorts of evidence that can be used to prove a crime, and there are also different types of evidence.

Evidence is either direct, it provides information that is beyond a reasonable doubt, or it's circumstantial, meaning that it may suggest proof, but doesn't absolutely prove something by itself.

If there is a bloody baseball bat that was used in the commission of the crime, that would be physical evidence. There's also, of course, eyewitness evidence. If a person witnessed a proportion of an offense, it would be eyewitness testimony.

There is circumstantial evidence where there may be no witnesses, there may be no physical evidence. But there are circumstances that make it so unlikely that anybody other than the person charged committed the crime.

Such as there was a break in to a place, items were stolen, the person charged was the person that just happened to be found a few minutes later with the stolen property. There's no direct evidence that that was the person who stole the property, but there certainly is circumstantial evidence.

Why? Why are we here today?

In legal cases, both direct and circumstantial evidence are usually presented. Once a case goes to court, jurors are told to decide what the facts are solely from the evidence admitted in the case, and not from suspicion or conjecture.

Yes, Mr. Ralphs is one of the other patrons at the bar.

Verbal or written testimony makes up a large portion of criminal evidence. Testimony can come from several sources, including the victim and the suspect. Some testimony may also come from forensic experts hired to analyze and present evidence and information about the crime.

Physical evidence, such as a weapon, is used to reconstruct the crime scene. It can be either direct or circumstantial, but physical evidence always involves tangible objects.

Depending on the particular crime scene, there may be evidence such as biological materials. Blood, for example. Or there may be drugs that were introduced into the crime scene as a result of the crime itself. But there's all other types of evidence that may not be obvious, such as what we call trace evidence.

These are fibers or hairs that are so small that it takes a microscope to determine that they're there in the first place. So evidence is such a broad scope. And again, it depends on the particular crime and the events associated with that particular crime.

Computers, smartphones, tablets. The everyday use of these devices means that the value of digital evidence recovered from them can be vital to solving a crime.

Vehicles store data on the event data recorders to monitor driver behaviors, including break application, steering, speed at time of impact in a crash, and whether the driver and passengers were using belts. Mobile phones are simply portable computers.

Many people store all sorts of important data about their life and activities on them, such as contacts, call logs, calendars, emails, text messages and GPS data. Digital evidence specialists have no trouble recovering information from these devices.

Every aspect of our life now is really dependent upon some form of digital device, communications. Some digital aspect. Everything we do now, as far as everything from surfing the internet to your cell phones, communications, emails, things that most everyone use leaves traces.

And it's our job as forensic analysts to take those traces and put them in a readable, and into an understandable format that the average investigator, judge and jury can understand. And actually use that information as part of an investigation, and as evidence and proof of a person's guilt or innocence.

While lawmakers struggle to catch up, judges and courts are taking wildly varying positions on the reliability and admissibility of digital evidence.

The role of judges has somewhat involved as our gate keeping role is there, it's always been there. But frankly, we are now required to determine whether or not some theories are actually junk science or not, and whether they should actually ever get to a jury.

The increasing use of digital evidence has spawned a new legal specialty, e-discovery, and has added layers of complexity that didn't exist when cases were won or lost on paper documents. In some cases, particularly those involving corporations, the amount of digital data that must be recovered and sorted through prior to trial is immense.

It tells exactly what the contents of each bag was.

It seems that electronic evidence is admitted in almost every trial in America these days, whether it's a phone bill or electric bill, or a document that's created, stored, or transmitted electronically.

Even a crime scene photograph is now considered electronic evidence. But the key point to remember about evidence, no matter what kind or type it is, is that it must be relevant to proving right or wrong in a court case.

The rules of evidence, which can vary from state to state, ultimately decide what evidence will be presented to the judge and jury for evaluation, and what evidence will not. Evidence may be evaluated in a variety of settings at various stages of the investigatory and criminal court process.

In the process of review and evaluation of evidence, weaker cases are filtered out of the system, or lesser charges are used. Prior to the trial, discovery is undertaken, where both the prosecution and the defense gather evidence through formal questions put to the other side.

Depositions of witnesses and examination of documents and records. Various motions can be filed by the parties as a result of discovery.

That is when all of us come together and get an understanding based on the motions that are presented as to what is left, or what is going to go forward and be heard by a jury.

So I think it's very important that there are pretrial motions brought forward, and determinations by the judge so that the lawyers can advise their clients what the issues are really going to be before the jury that they need to concentrate on.

When a case goes to trial, there are many ways in which evidence can be presented to a jury to help them understand the nature of what they're being told or shown. This might include video, photographs, pieces of physical evidence called exhibits, audio recordings, transcripts, maps, even handwriting samples and phone records.

Sometimes expert witnesses will be called in to give testimony. These people are often professors, doctors, or leading experts in a chosen field, such as audio engineers or computer technicians.

Witnesses, either in person or via video may present evidence in court, too. Confidential communication is also referred to as privileged information, and can be exempt from being used as evidence.

The only way a witness's testimony would be disallowed is if there was some privilege that would prevent the testimony. For instance, husband, wife privilege. A spouse can't testify against the other spouse, or can't be forced to testify against another spouse.

Some jurisdictions have physician, patient. Some have priest, pennant. That's the primary reason why testimony would be prohibited. Short of that, it's the job of the cross examiner to expose any problem with a witness's testimony.

Either that they've misperceived the facts, they've been inconsistent, they seem to be lying. Bias is not a grounds for refusing to allow a witness to testify. It just gets exposed on cross examination.

Evidence and the use of it is always meant to determine or demonstrate the truth of an assertion. Whether it is the assertion of the defense or the prosecution, the trick is collecting and documenting it correct, getting it admitted at trial, and using it to its best advantage. Evidence is the mainstay of the criminal justice system.

By relying on the proof created by reviewing criminal evidence, juries are more likely to have an objective, fact based understanding of a crime. Ideally, creating a justice system based on strict adherence to evidence laws will result in correct identification and consequences for criminals.