Research interview report:

Interviewee: Master Police Officer (MPO) Tara Crider – Arlington County Police Department


I interviewed a Master Police Officer, with our crime scene unit at the Arlington County Police Department. She investigates suspicious deaths, homicides, suicides, child deaths, fatal crashes, sexual assaults, burglary and any scene that involves a bloody fingerprint. MPO Crider stated she helps with any complex forensic work that our road agents (Corporals) are not trained to do. MPO Crider explained our patrol agents (Corporals) are responsible for processing burglaries, DOAs, destruction of property, assaults, etc. They are trained to process these patrol level cases that are not considered complex or outside of their expertise. 

Preservation of evidence

            I asked MPO Crider when processing outdoor crime scenes in different climates how it can affect the preservation of evidence. She stated when processing scenes during rain and/or snow it can potentially wash away evidence, such as DNA or shoeprints in mud. Whereas heat and humidity can denature DNA. Sometimes evidence cannot be recovered if it is destroyed. Even though, the evidence was destroyed she stated there is always other evidence but detailed notes/documentation as to why the evidence was destroyed is very pertinent information. It is also, important to take detailed notes when on scene especially notating the climate at the time of collection. However, even though the evidence might have been lost/damaged the pictures can still be used as evidence for that lost or damaged item.

Evidence collection

Locard’s exchange theory impacts the way she processes crime scenes. Locard’s theory indicates that there is always a trace evidence left behind at the scene (James, et al. 2014). MPO Crider gave the basic steps she follows when collecting and processing a scene.

a.         Take notes about the scene and evidence

b.         Sketch the scene and evidence locations

c.         Take measurements of the scene and evidence location (either by hand or via a laser measuring device – FARO)

d.         Photograph the scene and evidence

e.         Determine order of evidence collection – perishable items will be collected first, and then all other items are collected via a systematic working route through the scene.

f.          Proper packaging for each item is selected to preserve additional forensic evidence such as fingerprints and/or DNA.

In order to collect evidence proficiently, MPO Crider stated being able to work well with other team members is important. For example, one person can photograph the evidence, another person can take notes about the item and a third person can do the evidence collection. She stated they do not always have the luxury of working with others, so if working alone, the best way to be proficient is to stay organized. MPO Crider has a method as to how she processes scenes and uses the same method every time. It ensures she does not miss anything and can stay focused and finish the task in a timely manner.

            I asked MPO Crider does she process a homicide different from a suicide scene. She stated all death scenes are treated the same however, if evidence begins leaning towards a homicide versus a suicide their evidence collection process is different. For example, in a homicide case they are more likely to swab every light switch, faucet handle, etc. for DNA. Whereas a suicide they would not go to this extent to collect evidence.

            I asked MPO Crider if fingerprints could be collected from fabric clothing, she stated she has not heard of it being done before. However, pieces of clothing such as leather, or any like material they would likely use the powder process or chemically enhanced in the Cyanoacrylate (superglue) chamber. She also stated, patent fingerprints could be collected from fabric clothing, in this case they would collect or preserve the fingerprint by photographing it. They would then let the patent print air dry and package the clothing item to not disturb the print.

Autopsies and collecting evidence at the ME’s Office

            According to MPO Crider, autopsies are very important because the body is often the best piece of evidence there is. In Virginia, the body is jurisdiction of the ME, not the police. The police have jurisdiction over the scene only. They must work closely with the ME to get whatever additional information and/or evidence the body can provide. The ME will collect the additional evidence (buccal swabs, trace, etc.) from the body that either they think they need for the investigation or whatever the police request from them. Our MPO unit has a good working relationship with the ME’s Office, so they always assist in our requests.

            Identifying person(s) who are considered Jane/John Doe, are typically done by collecting their fingerprints by doing the print roll method. After the collection of the fingerprint, the fingerprint will then be entered into the system and with hopes the person has had their fingerprints collected before, in order to determine their identity. She stated if there are no matching fingerprints on file, or they are not able to obtain fingerprints from the deceased (badly decomposed), then they will resort to DNA or dental records. DNA or dental records can take days to months, depending on the backlog at the lab.            

Sending evidence to the state lab

            In order to send evidence to the state lab there are several forms that must be completed. A request for laboratory examination (RFLE) form must be completed for chain of custody. The evidence is then “checked out” of our property unit, which is cleared through LERMS. The RFLE and the evidence are then transported to the lab and turned over to the evidence receiving unit at the lab. The evidence receiving unit will ensure the item is packaged properly and labeled correctly. The evidence will then be entered into their system and handed over to the lab. The RFLE form stays with the item as it travels from evidence receiving to the analyst, etc. Chain of custody is important and therefore documenting where the item is going is crucial. Chain of custody can be questioned in court if there are any discrepancies (James, et al. 2014).


Crider, T., personal communication, Arlington County Police Department. Crime scene unit. May 18, 2020.

James, S., Nordby, J., & Bell, S., (2014). Forensic Science. An introduction to scientific and

investigative techniques.

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