Sequential Versus Simultaneous Line-Ups


Misidentification of suspects is one of the biggest challenges facing criminal justice system, because it often leads to wrongful convictions. Approximately 75% of convictions were annulled through DNA testing and, as a result, the justice system has been negatively impacted (Warmelink, 2015). Moreover, this problem can be traced back to wrong identification of suspects during the police investigation period. Therefore, due diligence on the part of the police will go a long way to ensure that the suspects brought to the court are the individuals that have been accurately identified by a thorough line-up session. The paper aims to discuss whether accurately identifying suspects will require the police to employ sequential line-ups.

Police Line-Ups

Line-ups entail police lining up the suspects among other people who are not active suspect in the case at hand (fillers) and then bringing the eyewitnesses to try and identify the culprit. This can be done live, in which case the suspect and the “fillers” are brought in and the eyewitnesses are asked to identify the suspect. On the other hand, line-ups can take the form of photographs (Schuster, 2007). The aim of line-ups is to help the police identify suspects with the help of eyewitnesses for the purpose of seeking justice.

Forms of Line-Ups

There are two forms of police line-ups, namely the simultaneous and the sequential one (Bartol, 2012). Simultaneous line-ups are a form of line-ups commonly used by police departments. Under this form, the eyewitness sees all the people involved or their photos at the same time. On the other hand, under sequential line-ups, the police show an eyewitness potential perpetrator or photos one at a time (Howitt, 2012).

Simultaneous line-ups have been the standard form of line-ups utilized by the police in many countries for identifying the suspect with the help of eyewitnesses. However, studies have shown that this form leads to a higher rate of misidentification leading to no convictions, since the DNA analysis discount the ‘suspect’ picked during the line-ups. This has compelled many people to assert that sequential line-ups ought to be the dominant form of line-ups utilized by the police.

Views against Simultaneous Line-Ups

The main argument against simultaneous line-ups is the fact the eyewitness uses ‘relative judgment’ (Schuster, 2007). This means that the witness at hand compares what he or she sees during the line-up internally rather than comparing what they view with memories of who committed the crime. The main downfall of this form of line-ups is the fact that in instances when a real perpetrator is present, the eyewitness is bound to choose a close resemblance of the offender leading to misidentification. When facing all the photos and people at the same time, eyewitness makes an effort to compare the individuals present rather than comparing each and every one with his/her memory pertaining to the incident being investigated. What this leads to is a situation, where the eyewitness is pressured into making a choice based on a distorted platform brought about by an overwhelming comparison session. This method, therefore, leads to eyewitnesses picking a person looking similar to who they saw rather than the one they actually saw, leading to misidentifications that in turn jeopardize the entire process of seeking justice for the victims. Therefore, the question at hand is, whether a sequential line-up is the answer to reducing misidentification incidences.

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Sequential Line-Ups

As mentioned, sequential line-ups entail presenting fillers and the suspect to the eyewitness one after the other. The advantage of using this approach is the fact that an eyewitness is exposed to potential suspects one at a time and the task is comparing the person at hand with the memories of the incident being investigated (Howitt, 2012). This means that an eyewitness has only two choices at any given time. They can either concur or disagree on whether the person in front of them is the suspect or not. Another advantage of this approach is that eyewitnesses are not overwhelmed in any way since the choice is less engaging as they only have to compare two people at the same time, what they can remember as the ‘suspect’ and the person being presented to them.

A study conducted in Charlotte-Mecklenburg (NC) Police Department, San Diego (CA) Police Department and Austin (TX) Police Department demonstrated that using the simultaneous approach, suspect identification success rate was at 25.5% (Wells, Steblay, & Dysart, 2011). On the other hand, using the sequential approach the success rate was pegged at 27.3%. Identification of fillers as suspects in simultaneous line-ups was at 18%, while at 12.2% in the sequential (Wells, Steblay, & Dysart, 2011). The results clearly indicate that utilizing sequential line-ups leads to a decreased rate of misidentification as compared to utilizing the simultaneous approach.

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The Illinois Study

In this study, the goal was to compare and contrast the success rate of sequential double-blind method versus the traditional simultaneous non-blind procedure. The results demonstrated that non-blind simultaneous approach produced better results than the double-blind sequential approach. However, there was an argument that the non-blind approach meant the policemen in the case knew the real suspects and could have influenced the eyewitness into identifying the real culprit (Wells, Steblay, & Dysart, 2011). These disagreements brought forward the need to have a thorough unbiased research into verifying the success rate between the sequential and simultaneous approaches. This necessitated the Greensboro Meeting in 2006 where professionals on matters of research, data analysis lawyers, and other relevant bodies were involved (Wells, Steblay, & Dysart, 2011). The aim was to come up with a level field between sequential and simultaneous procedure. Out of 497 line-ups, under the identified protocol the suspect identification was at 27.3% which was bigger than simultaneous’ 25.5% (SADO, 2016). Filler’ identification as suspects for sequential was at 12.2% which was less than 18.1% of the simultaneous line-ups. In addition, when N=288 “not sure” response for sequential equaled 46.5% as compared to 19.2% for simultaneous. The rejection rate for sequential was at 80.8% with 53.5% in simultaneous (Wells, Steblay, & Dysart, 2011).

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Insights from the Illinois Study

It is evident that sequential approach to conducting line-ups yielded better results than the common simultaneous approach. Moreover, the eyewitnesses were in a better position to make clearer decisions illustrated by the “not sure” response rate of 46.5% >19.3% (Wells, Steblay, & Dysart, 2011). This demonstrates that in the sequential approach eyewitnesses had a clearer comparison between what is and what is not true regarding the suspect. Moreover, rejection rate in the sequential (80.8%) was higher than in simultaneous (53.5%) (Wells, Steblay, & Dysart, 2011). This demonstrates that the confidence level of an eyewitness identifying the absence of a suspect was higher in sequential approach as compared to simultaneous. Over and above, the mistake of identifying fillers as suspects proves the greatest strength of utilizing the sequential approach. Under the sequential approach, this error was significantly lower than that of simultaneous 12.2% < 18.1% (Wells, Steblay, & Dysart, 2011). These insights clearly present sequential line-ups as superior to simultaneous line-ups.


The problem at hand is misidentification of suspects leading to the lack of convictions and, as a result, increased jeopardy to the criminal justice system (Alison & Rainbow, 2011). The primary cause of misidentification is the poor judgment of eyewitnesses, a phenomenon that affects the credibility of cases in any court. Therefore, in order to minimize the occurrence of misjudgement by the eyewitness the police should utilize the approach that yields the highest accuracy. It is evident, that under the same conditions the sequential approach is more accurate than simultaneous regarding suspect identification and minimization of filler identification (Wells, Steblay, & Dysart, 2011).

In this case, based on the statistics one of the principal causes of misidentification is picking a filler subject as a suspect. Moreover, it is also evident that the problem of eyewitnesses picking a filler as a suspect is more common in simultaneous approach at 18.3% as compared to the sequential’12.2% (Wells, Steblay, & Dysart, 2011). This signifies a difference of 5.1% of accuracy if the sequential approach is to be utilized. All these parameters present sequential line-ups as the better option when it comes to identification of suspects.


It is evident that sequential line-ups present an accurate manner of conducting police line-ups based on the improved level of accuracy and confidence level of eyewitnesses making certain decisions when the sequential line-up method is utilized. It is also evident that sequential line-ups have minimized errors in terms of misidentification brought about by identifying fillers as suspects. Overall, it is clear that the police should employ more effort in utilizing the sequential approach of identifying suspects as this will lead to an improved positive suspect identification.

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