Recent Discovery Trends for DUI Cases

For many years, prosecutors have possessed an unfair advantage in the area of investigative resources. Having an unlimited budget has allowed prosecutors to use inexhaustible resources in finding every possible shred of evidence that might be remotely related to a criminal investigation.

That unfair advantage is gradually shifting and balancing to give defendants more tools. Years ago, the use of hand held video recorders was something only used by the Central Intelligence Agency (CIA) and seen in James Bond Movies; but now, everybody with a cellular phone has the ability to take a video of anybody at any time.

Furthermore, with specific regard to prosecuting DUI’s – the technology used to prosecute and convict somebody for a DUI hasn’t changed in years. Most law enforcement agencies are still using the DataMaster or the Intoxilyzer to test breath despite the huge body of evidence demonstrating blood tests to be inherently more reliable.

If law enforcement agencies choose not to use technological advancements to prosecute criminal cases – including DUI’s – then an opportunity is provided to defense attorneys to balance the playing field by using their own technology to advance the interests and defenses of their clients. Smart attorneys are taking advantage of technology and challenging the traditional views of what constitutes “discoverable evidence.” No longer is discovery limited to a piece of paper handed to you by a prosecuting attorney.

Most attorneys with clients charged with DUI have a substantial number of evidentiary options because of technology. Defense attorneys should be using that technology to help defend their clients. The technology available to help a client can exist in many forms and its use is only limited by the creativity of the attorney representing the client.

The traditional views of discovery and technology rarely move beyond obtaining a video recording from a cop car, and many attorneys have been complacent or happy with having a video which may or may not demonstrate the innocence of their client. However, with today’s advancements in technology, attorneys should be taking advantage of other technology in the form of independent medical opinions, independent witnesses, or audio and video from independent sources and witnesses.

The use of technology in the defense of a client charged with a DUI is only limited by the imagination and budget of the attorney.

With regard to discovery requests, historically the standard evidence provided by a prosecutor in a routine DUI case include police reports and the maintenance reports for the breath machine. Although those may be the normal items provided, defense attorneys should, at a minimum, be requesting additional items, including, but not limited to: videos of the stop, recordings of any conversations between the arresting officer and dispatch, private cellular phone records from the arresting officer, the user or operator manual for the breath machine used to test the breath, and a copy of all possible reports produced by the breath machine.

When facing such requests from a defense attorney, most prosecuting attorneys will refuse to make any effort to obtain the requested materials, and they will argue the state statute(s) governing discovery only requires disclosure of materials in their actual possession. In those situations, the use of subpoenas, subpoenas duces tecum and requests for production of documents may be used to compel record keepers to produce the materials necessary to defend a client.

If a hearing before a judge is needed, your arguments for production of the relevant materials should be based in the rights afforded by the 5 th and 6 th Amendments of the United States Constitution (as discussed in Brady v. Maryland) along with any state statutes or state case law relevant to the issue. Prior to such hearings, a motion should be filed and ruled upon by the court to make certain the prosecutors brings the requested materials to court – so at the very least – the court can do an in camera hearing to determine whether or not the items sought constitute Brady materials. Such a hearing also preserves the issue for an appeal.

Videos of the Stop: A large number of jurisdictions use video and/or audio recorders to capture interaction between officers and suspects. The video and audio recordings are extremely important and should be examined closely to see if the details in the videos match the events described in police reports or as testified to while under oath and subject to cross-examination. In all cases, attorneys should look at videos to determine if the client exhibits signs of intoxication. Any such signs of intoxication should be compared to signs noted by the officer in his or her report. Usual signs of intoxication listed in police reports include, but are not limited to, the following:

1. Whether the defendant properly responds to verbal requests.

2. Whether the defendant has difficulty following instructions.

3. Whether the defendant is able to walk without stumbling or assistance.

4. Whether the defendant’s voice is slurred or difficult to understand.

In cases where field sobriety tests are given, defense attorneys should use any video or audio to ensure proper procedures were followed when administering Standardized Field Sobriety Tests. The National Highway Traffic Safety Administration produces annual training manuals used by law enforcement agencies to train and certify officers to properly give field sobriety tests. Those annual manuals contain the necessary procedures to be followed in order for the results of a field sobriety test to be considered valid, reliable, and therefore admissible in a court of law.

As an example, The National Highway Traffic Safety Administration (NHTSA) provides that the following formal instructions are to be given to a person prior to performing nine-step walk and turn:

5. Place your left foot on the line (real or imaginary).

6. Place your right foot on the line ahead of the left foot, with the hell of your right foot against the toe of the left foot.

7. Place your arms down at your sides.

8. Maintain this position until I have completed the instructions. Do not start to walk until told to do so.

9. Do you understand the instructions thus far? (Make sure the subject indicates understanding).

10. When I tell you to start, take nine heel to toe steps on the line, turn, and take nine heel to toe steps down the line.

11. When you turn, keep the front foot on the line, and turn by taking a series of small steps with the other foot.

12. When you are walking, keep your arms at your sides, watch your feet at all times and count your steps out loud.

13. Once you start walking, don’t stop until you have completed the test.

14. Do you understand the instructions (Make sure the subject understands). [i]

We have all had cases where those exact instructions were not given before a law enforcement officer asked a suspect to do the nine-step walk and turn test. I do not believe that a court will grant a Motion to Suppress or Motion in Limine for the failure to follow those instructions verbatim, but the main principles should be articulated by law enforcement and the failure to do so should result in a motion to suppress.

A checklist containing the necessary requirements – and clues for failure – can be helpful when determining whether proper procedures were followed in your case. In the event proper procedures were not followed, a pretrial Motion to Suppress or Motion in Limine is proper. Similar checklists can and should be used to determine the following:

  • Whether a preliminary breath test was properly administered
  • Whether sufficient facts exist to establish probable cause for arrest
  • Whether the proper procedures were followed when providing a breath or blood sample

In response to any such motions, the prosecutor is likely to argue that the failure to follow the proper methods goes to the weight to be given to the evidence as opposed to the admissibility. In those cases, it may be necessary to use the training manuals and testimony from law enforcement to demonstrate that the failure to follow the proper steps renders the results completely invalid.

In the event that video and/or audio are unavailable – despite the fact law enforcement had the ability to record an interaction with a defendant – a pretrial Motion to Suppress or Motion in Limine should be filed noting any statutes or administrative regulations requiring electronic recording. Furthermore, suppression based upon spoliation is always necessary when law enforcement could have recorded an interaction with a defendant but did not because of technological problems or human error.

Materials from NHTSA: As noted, the National Highway Traffic Safety Administration is the agency responsible for setting the standards for Field Sobriety Tests. Any defense attorney doing DUI work should have a set of yearly manuals for the past several years.

Using the manuals to impeach an officer is very important and can lead to suppression of field sobriety tests or can be used to demonstrate to a jury the results of any test should be given no weight if not done properly.

In jurisdiction allowing depositions, a subpoena duces tecum should be used to have the officer bring any training materials he still possesses. At the very least, during a deposition, you should always get the officer to look at a training manual and concede the following points:

15. The officer was trained to administer field sobriety tests.

16. The materials used to train were produced by NHTSA.

17. He or she was taught that there are only three tests which have been scientifically correlated to alcohol impairment:

  • Horizontal Gaze Nystagmus Test
  • Nine Step Walk and Turn Test
  • One-Leg Stand Test

18. He or she was taught that the failure to properly follow the procedures outlined during training would impact the reliability of the test results. If necessary, show the officer the manual and use the language from the manual.

a. Laboratory research indicated that three of these tests, when administered in a standardized manner , were a highly accurate and reliable battery of tests for distinguishing BACs at or above 0.10; Horizontal Gaze Nystagmus (HGN), Walk and Turn (WAT), and One Leg Stand (OLS). NHTSA, DWI Detection and Standardized Field Sobriety Testing, Student Manual, March 2013. (Emphasis provided).

19. He or she always follows the proper procedures when performing the HGN test or asking a suspect to perform the Nine Step Walk and Turn Test or the One-Leg Stand Test.

20. He or she agrees if the procedures weren’t followed, the results should not be relied upon.

Then of course, your job is to demonstrate – either through the officer’s testimony or a video – that the proper procedures were not followed and the results of the field sobriety tests can not be considered reliable.

NHTSA also has produced materials specific to the HGN test – the most reliable of FSTS – which indicate the failure to follow the specific procedures can result in false positive tests. The Robustness of the Horizontal Gaze Nystagmus Test was an extensive study which essentially led to the conclusion if an officer moved a stimulus too fast across a suspects face when performing the HGN test, a false positive test was likely to result. The same was true if the stimulus was held too high or too low – not right at a suspect’s eye level.

Using the materials produced by NHSTA is a very effective method of suppressing the results of field sobriety tests or, at the very least, demonstrating to a jury that the results should be given no weight in determining whether a defendant is under the influence of alcohol.

Recordings from Independent Sources: Investigating the area and place where a traffic stop occurred for a DUI arrest is extremely important. All criminal defense attorneys have had situations where they believe law enforcement was lying or embellishing the grounds for a traffic stop that ultimately led to a DUI arrest. In those situations, it is important to visit the scene of the traffic stop and make an independent assessment of the facts and circumstances leading to the stop.

While investigating the scene, it’s possible to find recordings from other sources that may help your client’s case. Restaurants, convenience stores, private business and private homes frequently have security cameras and most are willing to provide copies of any relevant footage. Independent video can be used to impeach an officer’s testimony and prove a person did not commit a traffic violation (e.g., run a red light, roll through a stop sign, fail to use a signal, or make a wide turn, etc.). In addition, such video can also be used to impeach the officer’s testimony regarding his observations about the defendant’s signs of intoxication.

Furthermore, by visiting the scene, you are able to understand the perspective of your client and that perspective can help generate relevant evidence to help suppress the stop, detention or tests. Sometimes it is beneficial use your cell-phone to take pictures or video of the area associated with the stop or make a video the route driven by your client prior to the stop in order to develop grounds to suppress the stop and detention. Of course, an attorney cannot lay the foundation for his own video or pictures so a private investigator, law clerk or other person may be needed to take the pictures or record the video and testify to the foundational requirements to offer the items into evidence.

Recordings of Conversations between the Officer and Dispatch: Within most jurisdictions, electronic recordings are kept of the conversations between officers and dispatch. Whenever handling a DUI case, it is important to try to obtain recordings of those conversations to ensure there is sufficient probable cause for the traffic stop. In many cases, officers may provide a reason for a traffic stop when reporting their location back to the station. At times, the reasons verbally articulated by the arresting officer do not match the reasons stated to the driver or the actual evidence within the video. As an example, if the officer self-reports to the station the reason for a traffic stop is “failure to use a signal”, but the officer tells a driver the basis for the stop is speeding, a pretrial motion is necessary. Also, the conversations between law enforcement and dispatch usually contain date and time stamps. Occasionally the location and time provided in the audio recordings establishes a defense of “factually impossibility” if those dates and times conflict with those reported by the officer or recorded on the officer’s dash camera. Restated, occasionally, the dates and times listed in the recordings between an officer and dispatch may vary from the dates and times either listed by the officer in his own reports or as stamped on the video from the officer’s in-car camera. In the case where the dates and/or times vary substantially, many arguments can be made including “factual impossibility.” (E.g., it would have been impossible for law enforcement to have observed the traffic infraction at the date and time listed in their own reports or on their own dash cameras).

Cellular Phone Records from the Arresting Officer: In jurisdictions allowing depositions for misdemeanor or felony DUI cases, one of the questions to be asked of the arresting officer is whether he or she has a private cellular phone, the private carrier for the phone service and the actual private cellular phone number.

Questions should also be asked to determine whether the officer uses his private cellular phone for work purpose and whether the private phone was used at any point during the pre-arrest, detention, or arrest of the defendant. Occasionally, a defense attorney will find that an officer may have used his phone to text another officer or send a message to a wife or husband. Although not by itself relevant to suppression, if the texts or messages were sent during the pre-arrest, detention or arrest phase, such information can lead to suppression of evidence. Several breath testing devices used for DUI prosecutions involve observation where officers are required to observe a suspect to ensure the person does not burp, belch, vomit, or place anything into his or her mouth. Affirmative evidence in the form of text messages can be used to prove an officer did not follow a mandatory observation period and can provide the basis for a pretrial motion to suppress. As an example, if a series of text messages was sent and received during a mandatory 15 minute waiting period, a defense attorney can argue that it was impossible for the officer to “observe” the defendant continuously for 15 minutes if, during that 15 minute period of time, the officer exchanged several text messages with his wife or a co-worker.

Furthermore, the reliability of many breath testing devices is impacted by the use of electronic devices. Many jurisdictions have rules or regulations in place to prohibit the presence of active police radios, cellular telephones and other devices in or near breath testing machines.

[i]. DWI Detection and Standardized Field Sobriety Testing, March 2013, Participant Guide, NHTSA.

Aside from the reasons discussed, there is a more scientific reason that law enforcement agencies have established rules which prohibit the use of electronic devices in or around breath testing machines. In short, other electronic devices can interfere with breath machines and impact the reliability of breath tests. Electromagnetic interference (or EMI, also called radio‑frequency interference or RFI when in high frequency or radio frequency) is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. [i] Radio-frequency interference may interrupt, obstruct, or otherwise degrade or limit the effective performance of an electronic circuit. These effects can range from a simple degradation of data to a total loss of data. [iii]

Breath testing devices such as the Datamaster and the Intoxilyzer obviously use electricity for a variety of functions: automate the measurement process, generate the light needed to shine through the chambers, to control and measure the flow of breath, to detect how much light reaches the detectors in the machines, to amplify the electrical signal, and to accept inputs from the keyboard and print the results. [iv] All of the electrical processes require an environment free of electromagnetic fields, in order to accurately and reliably measure and report the alcohol content in the subject’s breath. [v] If interference is present when an electrical component is actively engaged in one of the functions necessary to a breath test, then a malfunction of that electrical component can cause an error in the machine’s performance. [vi]

As an example, electricity is used to transmit infrared light from the infrared source at one end of a sample breath chamber to the other end – while being bounced off of four mirrors. If there is radio-frequency interference in the area when a sample is tested, it is quite possible that the radio-frequency interference can impact the initial level of energy produced by the infrared source at the start of the test. Since the breath testing devices measure the amount of infrared light received in a detector, a reduced level of energy produced at the beginning of the test may lead to inaccurate results. As a simple analogy, if you have an electric light bulb in your home, other electrical devices or other devices on the same circuit may impact the level of lumination of that light bulb. The same principle can apply to the infrared light used in the breath testing machines when radio-frequency interference is present.

In short, breath machines – and their subsequent results – can be impacted by devices that use certain radio frequencies.

Some older studies suggest that breath testing machines are not impacted by devices using radio frequencies between 30 – 2500 MHZ; [vii] however, many of the electronic devices currently using radio frequencies operate on much higher levels. Further, even if you believe the validity of those studies, in 2013, nearly 650 different devices were authorized to operate at a radio frequence band higher than 2500 MHZ. [viii] As an example, Samsung has several products currently on the market that operate at 2600 MHZ. [ix] At this point, no reliability tests have been done on breath machines to determine whether electronic devices operating at radio frequencies above 2500 MHZ impact the reliability of the results of breath testing devices.

Significantly, a recent case from the Ohio Supreme Court affirmed a lower court’s decision finding the results of Intoxilyzer 8000 unreliable, in part, because the state failed to produce radio interference records pertaining to the machine. [x]

Of course, nearly all law enforcement officers have a radio on their person at all times. All defense attorneys would benefit from determining the radio frequency used by police radios in their respective jurisdictions and whether the use may interfere with the results of a breath test.

Finally, the DataMaster DMT has a setting where the operator can adjust Radio Frequency Interference Detection sensitivity level. (See, Figure 1). Certainly it would benefit law enforcement to adjust the detection sensitivity level to as low as possible as to make certain any breath tests are not impacted by hand held radios, cellular phones or any other electronic devices near or around the breath testing device.

In jurisdictions using the DataMaster DMT, attorneys should be asking for records relating to the Radio Frequency Interference Detection sensitivity level. At the very least, attorneys should be filing motions demanding the opportunity access to the DataMaster DMT to determine the Radio Frequency Interference Detection sensitivity level setting and whether any electronic devices in the area produce Radio Frequency Interference in the range addressed by the setting on the machine.

Records from the machine used to test the breath

Most defense attorneys routinely receive maintenance records associated with breath testing devices. However, attorneys rarely seek other reports from the same machines.

As an example, the DataMaster DMT is capable of producing the following reports:

  • Last Test Reprint
  • Options Settings
  • Calibration Factors
  • Breath Test Records
  • Calibration Records
  • Diagnostic Tests
  • Supervisor (Simulator) Tests

Although the DataMaster DMT is capable of producing several reports that could provide exculpatory information for a Defendant charged with DUI, several paired down versions of the software that come installed on the DataMaster do not produce all possible reports. Simply restated, law enforcement can purchase less expensive DataMaster machines that do not produce all possible reports.

If you live in a jurisdiction where the breath testing device is capable of producing reports but you do not get them as a matter of routine course through discovery, a subpoena duces tecum should be served upon the records keeper.

As an example, the “Breath Test Record” function of the DataMaster will allow access to several of the last breath test results given (e.g., 100, 150, etc.). Although the reports are available, most prosecutors will not provide those reports without a subpoena and a court hearing. If a prosecutor does not give you all the reports produced by your machine, a subpoena should be used to try and get those available records because they may contain information beneficial to your client.

The reports from prior tests are relevant to determine whether the test given to your client was reliable. If, for instance, if there was an error during the test prior to the one given by your client, the existence of that error may lead to information providing the basis to suppress your client’s test. If the error involved a “faulty temperature” or “radio frequency interference”, a motion to suppress may be appropriate if the machine was not properly calibrated before being placed back into operation.

If you live in a jurisdiction where the breath testing device is a less expensive version that does not produce all possible reports, a motion to suppress based upon spoliation could convince a judge to suppress the results. Within the motion, an argument should be made that the State has a duty under Brady v. Maryland to maintain in its custody any evidence which is exculpatory to the Defendant, and the State’s failure to perform an act which would have saved exculpatory evidence (purchasing the full version of the software, etc.) is a violation of the duty articulated by the United States Supreme Court in Brady v. Maryland. Furthermore, under certain circumstances, the Due Process Clause of the 14th Amendment may require that the State preserve potentially exculpatory evidence on behalf of a defendant. See, e.g., California v. Trombetta, 467 U.S. 479, 104 S.Ct. 2528, 81 L.Ed.2d 413 (1984).

The User Manual for the Breath Machine

One thing that every DUI defense attorney should possess is a copy of the user manual for the Breath Testing Device used in the jurisdictions where they practice. Most user manuals can be found online.

At a minimum, user manuals frequently detail the initial set up of the machine, regular calibration procedures, proper instructions for testing a subject, a list of error codes and their meaning, and the proper way to analyze the results.

As an example, some user manuals will specifically show pictures of breath sample graphs and how to properly interpret them. (See, Figure 2). In the example provided, the manual indicates that a person providing a non-continuous breath pattern would produce a graph that is up and down. The manual also provides such a result should be an “invalid sample” and in many jurisdictions, this would constitute a separate charge for refusal to submit to a chemical test.

Figure 3 is an actual example of a fluctuating breath sample from the DataMaster DTM. In these types of cases, it may be beneficial to have a medical doctor examine the defendant to see if any medical conditions exist which would make it impossible to provide a continuous breath sample (e.g., Chronic Obstructive Pulmonary Disease, etc.). The doctor can also provide a medical explanation for the fluctuations in the breath sample as noted in Figure 3.

The steps outlined in the user manuals can be incorporated into a check list to ensure that the proper procedure is followed for the tests given to your clients.

Medical Examination of the Defendant: When obtaining a medical examination of a client, consideration should be given diseases or disabilities diagnosed.

Diabetes: For Defendants charged with DUI, some complications of diabetes may lead to inflated results.

Diabetic ketoacidosis is a serious complication of diabetes that occurs when somebody with diabetes produces high levels of blood acids called ketones.

Diabetic ketoacidosis develops when a person’s body is unable to produce enough insulin. Insulin normally plays a key role in helping sugar (glucose) — a major source of energy for muscles and other tissues — enter blood cells. Without enough insulin, a person’s body begins to break down fat as an alternate fuel. This process produces a buildup of toxic acids in the bloodstream called ketones. The process can eventually lead to diabetic ketoacidosis if untreated.

Although no studies suggest insulin impacts the results of a breath testing device, there is evidence to suggest that if a defendant is in ketoacidosis – the process of the body generating ketones – and the levels of ketones are high enough, the breath testing device may not function properly resulting in a mistaken belief the defendant failed the test. [xi]

Specifically, if a breath testing device used does not specifically account for abortion of infrared light by ketones, the breath test result may be artificially inflated because the ketones act like alcohol molecules.

Breathing Disorders: Another medical problem that could lead to inflated BAC exits for people with breathing disorders. Most modern breath machines have a minimum exhalation requirement before testing the breath for the presence of alcohol; a minimum volume of 1.1 and 1.5 liters of breath must be obtained. Once the minimum volume is reached, testing of the breath occurs.

While providing a breath sample, a defendant can stop producing a sample after the minimum volume is obtained but may continue to provide a sample until the maximum amount of breath is exhaled from the lungs.

The maximum lung capacity of a particular individual can vary from as low as 2.9 liters 5.0 liters. [xii] For a health adult male with a large lung capacity, providing more liters of air into the breath testing chamber naturally results in a lower breath alcohol reading as compared to a petite woman with smaller lung capacity. As an example, a healthy adult male may meet the 1.5 liter requirement of the breath chamber with forty percent (40%) of the maximum amount of breath exhaled from his lungs. Conversely, a petite woman may have to exhale at least seventy-percent (70%) of her breath capacity to meet the 1.5 liter requirement.

As noted by recent studies, the BAC results of those two individuals will vary. Restated, two individuals with the same blood alcohol content may have differing results on a breath machine if the lung capacities of the two individuals is different and a different proportion of air is exhaled from the lung. [xiii]

Researching the Arresting Officer

Another area of potential research frequently overlooked involves simple searches in online databases for information which can be used to discredit the arresting officer. If you are able to access orders from your local courts, a search of those order can produce instances of a court finding the testimony of an officer to be incredible or unbelievable.

Federal courts opinions can be searched for any such orders.

As an example, I’ve found opinions within my jurisdiction that discredit the testimony of law enforcement officers. If the facts of the prior case are similar to the facts of the current case (e.g., stop involves a minority and the reasons for the stop are tenuous at best, etc.), the prior determination by another court discrediting the testimony of the officer provides substantial weight that the officer may be lying in the current case.

Finally, seeking out disciplinary records for an arresting officer may provide underlying biases or other information which could be relevant to the particular facts in your client’s case.

If you are fortunate to find both an opinion about the credibility of an officer along with disciplinary records, the combination of those two items can be powerful tools to convince a jury an officer’s opinion regarding intoxication is simply not true.

[i]. DWI Detection and Standardized Field Sobriety Testing, March 2013, Participant Guide, NHTSA.


[iii]. Sue, M.K. “Radio frequency interference at the geostationary orbit”. NASA. Jet Propulsion Laboratory. Retrieved 6 October 2011.

[iv]. TAYLOR & OBERMAN, DRUNK DRIVING DEFENSE (7th ed. 2010) at 588-599.

[v]. TAYLOR & OBERMAN, DRUNK DRIVING DEFENSE (7th ed. 2010) at 588-589.

[vi]. TAYLOR & OBERMAN, DRUNK DRIVING DEFENSE (7th ed. 2010) at 588-589.

[vii]. Georgia Breath Testing Evaluation, September 2012



[x]Cincinnati v. Ilg, 141 Ohio St.3d 22, 2014‑Ohio‑4258.

[xi]Interfering Substances Identified in the Breath of Drinking Drivers with Intoxilyzer 5000, A.W. Jones, Lars Andersson, Karin Burglund, Journal of Analytical Technology, Vol. 20, Nov/Dec. 1996.



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