Last Updated on May 11, 2022 by Fair Punishment Team

If you have been involved in either a criminal investigation, either through no fault of your own, a mistake made by your or your family members or as the victim of crime, then you might feel shaken. The processes by which law enforcers work are at times somewhat brutal and have a tendency to dehumanize them to everyday crime situations in which ordinary people like you or me might feel shocked or nervous. 

The process of examining evidence or speaking to witnesses may be normal for them but for us it is anything but normal. That’s why if you are in a stressful situation such as a criminal investigation it is important to understand how the system that you are working with works. 

That’s what this piece will aim to do – explain to you exactly what some of the processes involved in a police investigation are, how they work and why they exist. No longer will you be wondering “What is chain of custody” or “How does a chain of custody work” because you will already have the answers. 

What is chain of custody 

First of all, let’s explain exactly what a chain of custody is. A chain of custody is the process by which evidence, potentially items collected from a person’s house but at times also including files from their computer or cell phone, is process down a line from the evidence gathers to those who analyse the evidence to, if the evidence if found to be of important to a criminal case, eventually the lawyers of both the state prosecutors and the defendant’s lawyers. 

The chain of custody is vitally important to follow for several reasons. Firstly, it is important because it ensures that due procedure has been correctly followed. What this means is that the evidence can clearly be seen to have originated from one source, been passed to another for analysis before being passed on to the courts to be used in trial if found to be relevant. 

The chain of custody acts as a golden thread by which the evidence can be seen to be linked back from either a person that is believed to be connected to the crime or the crime scene itself and linked up to the person the police believe to be guilty. It is vitally important that the chain of custody exists and is properly followed because otherwise there could be accusations that the evidence has been manufactured or that it could have potentially tampered with. 

The chain of custody helps both prosecution and defense because it establishes, beyond doubt, the exact sequence of events that led to the items being taken, investigated and then analysed, meaning that if the evidence had been tampered with or the defense believe that the sequence of evidence hasn’t been fully explained to the court and wish to imply that it may have been contaminated, deliberately or accidentally, then the chain of custody can show who might have been responsible and also who is able to say one way or the other what happened to the evidence. 

Now that we have fully explained what the chain of custody is, let’s explain how exactly it works. 

How does the chain of custody work?

Let’s begin by explaining exactly how the chain of custody works. Unlike in other parts of American life, where certain procedures are done differently in different states, the chain of custody universally applies to all law enforcement institutes across the United States and is therefore applicable to the entire country. You will not find radically different chains of custody from one state to another. 

Let’s set out the exact sequence of events that will occur with a chain of custody. 

To begin with, a police officer at a crime scene might notice something that they believe to be important. They will call over a police photographer who will photograph the piece of evidence in situ. It is important that there is evidence of where and when the item was found and how it was either lying on the ground or on a shelf so it can be clear where the item was, who found it, and in what circumstances it was found. 

Once the item has been photographed and the time of which it was found and by whom is noted down, the police office will use a sealed evidence bag to put the evidence in. This is important to prevent cross contamination and also for it to be clear that when the evidence leaves the scene it is not in any way open to contamination or even that it may be possible to switch out for another similar looking item. 

This is where the chain of custody forms and the chain of custody becomes vitally important. The reason for this is that every officer who handles a piece of evidence has to be documented and exactly what they did with the evidence has to as well because otherwise it could be suggested that the chain of custody has in some way been broken and the item potentially tampered with. 

What should happen is that either the officer who found the item should take it to a scientific lab to be properly processed or, if another officer takes it, then it should be logged as to which officer took it, the amount of time it was in their possession and when they arrived at the station to either log the item in or when they arrived at the lab and when the item was logged in there. 

The reason that this is so important is because if an officer asks someone else to take the piece of evidence in to be analysed by another officer and they fail to note down who that officer was, what time they took the piece of evidence, how long it was in their possession for and at what time they discharged the evidence from their care, then the evidence can become useless. 

No matter how compelling the piece of evidence is, no matter how vital it could be to the case, if the chain of custody is not properly followed then the evidence could be said to have been interfered with or that it was in some way planted or not the same as when it left the scene of the crime. This is why the chain of custody is so vitally important to follow because without it, criminal proceedings can become either untenable or much more difficult for both prosecution and defense. 

Once the piece of evidence has left the scene of the crime it should go, as soon as possible and preferably taken by the officer that found it, to a police forensic technician. The exchange of evidence must be outside of the actual lab itself or handled by someone who was not directly at the crime scene. 

It is important that the officer at the crime scene does not go into the police forensics lab with the piece of evidence themselves, particularly if they have just come from the crime scene as they could inadvertently contaminate the lab and render the evidence once again either useless or nowhere near as effective as it should or could be. 

Once the police forensic technician has received the item, they can then begin analysis. The type of analysis done will depend on the forensic technician and it will depend on what they hope to extract from the particular piece of evidence. For example, if the evidence is a computer then the evidence will be analysed by a computer technician to see what can be found on it potentially relevant to the crime that the police believe has been committed. 

Similarly, if the piece of evidence is a gun then a forensic gun technician will examine the gun and see if they can tell not only when the gun was last fired but if the calibre of the weapon matches that that was used in the crime. All of this information will then be recorded, processed and further analysed by the police technicians to see if there is any evidence linked to the crime. The object of the technicians is simply to reproduce the evidence that they find, not say one way or another as to whether or not the evidence really proves someone guilty or innocent. They are, above all, impartial, and therefore only simply meant to present the evidence as they find it. 

Once they have thoroughly analysed the evidence, a report will be produced to be passed along to the police officers working the case detailing the forensic technician’s findings and what they believe that evidence says. This may state that the calibre of the gun either matches or doesn’t match the gun used in the crime or that the computer contains or doesn’t contain any incriminating evidence. 

Once the report has been completed and handed over to the relevant authorities, the item of evidence is then handed back to the police. However, it isn’t handed back to the actual officers investigating the case but rather to a police evidence technician. 

Police evidence technicians are particularly important in the accurate line of the chain of custody because they handle the evidence when it has been looked at by the scientists and is ready to be stored away for trial. This is of course if the evidence is found to have a link to the case and be in some way incriminating – if the piece of evidence has been found to have no link to the crime and or nothing incriminating related to it then it is returned to the original owner. 

If however it is clear that the evidence is linked to the crime then it will be stored by a police evidence technician in a police evidence room. The police evidence technician is responsible for ensuring that the chain of custody isn’t broken and that anyone who wishes the request to see evidence is noted and that the reason they wish to see the evidence is noted as well. 

Sometimes defense attorney’s may request that evidence that is being used against their clients in a prosecution be tested by scientists that they are employing. This is perfectly natural however the police evidence technician must ensure that they note down when the evidence has been handled properly and to whom the evidence has been released. 

Eventually, if the case goes to trial, then the evidence will likely be called up to be used either by the defense or prosecution. The jury may also request to see the evidence which is why the chain of custody is so important – it ensures that when the jury comes to make their verdict, they can say that the evidence that has been presented to them has not been tampered with nor that it has been in any way supplanted.

Why understanding the chain of custody is so important 

The chain of custody is vitally important for you to understand because it is such a pivotal part of the legal process. 

Whether you become involved in a case, or a member of your family becomes involved in a case, it is vitally important that you know where an item that might be yours might be and how it might be being handled. 

Evidence doesn’t have to directly related to a criminal or crime to be a part of the chain of custody; if your house has been burgled and the police find the items that have been stolen then they will become part of a chain of custody for use in a trial as evidence of theft and you will have done nothing wrong. 

By understanding how and why the chain of custody works you are able to ensure that you have power in a system that may feel very unfamiliar to you and somewhat frightening. The legal system can be complex and make you feel very small if you don’t understand it, which is why, if you ever have to become involved in a criminal case, you need to understand exactly what is happening at all times, not just for you but for your family and friends. 

The law is meant to be there to aid and help ordinary people so make sure that it does exactly that for you.