Polygraph Test Preparation: Night Before Checklist

The Science Behind Pre-Test Preparation

A polygraph examination measures involuntary physiological responses — changes in respiration, cardiovascular activity, and electrodermal (skin conductance) responses — that occur when a person is asked relevant questions [1]Verified Effect of the Stimulation Test Administered Before and After the First Relevant Chart of the Control Question Test
Confirms how stimulation test timing influences examinee psychological set and physiological response patterns. Your examiner uses these measurements to assess whether deceptive responses are present. What most people don't realize is that the quality and interpretability of these measurements is directly influenced by your physical and mental state when you walk into the examination room.

Modern computerized polygraph systems are extraordinarily sensitive. They can detect changes in breathing depth, blood pressure shifts of just a few mmHg, and skin conductance variations measured in micro-siemens. When your body is well-rested, properly nourished, and free from chemical interference, these instruments can establish a clean physiological baseline. Your normal, truthful responses look distinct from any deceptive responses, giving the examiner the clearest possible data to work with [2]Verified The contribution of the dorsolateral prefrontal cortex to the preparation for deception and truth-telling
Confirms that the left DLPFC is more activated during lie preparation than truth preparation.

Conversely, when you arrive sleep-deprived, over-caffeinated, hungry, or highly agitated, your physiological baseline becomes erratic. Your body is already in a state of stress, and the instruments have a harder time distinguishing between your general distress and any specific reactions to test questions. Experienced examiners are trained to account for various conditions, but proper preparation helps ensure you get the most accurate, defensible results possible [3]Verified Preparation to Experimental Testing of the Potential from Using Facial Temperature Changes Registered with an Infrared Camera in Lie Detection
Foundational research relevant to alternative physiological measurement methods in deception detection. Research has confirmed that stimulation test timing and examinee psychological set directly influence physiological response patterns to relevant and comparison questions [4]Verified Effects of sleep deprivation on heart rate variability: a systematic review and meta-analysis
Confirms sleep deprivation impairs cardiac autonomic function with sympathetic predominance and vagal suppression.

If you're interested in understanding the full testing process before focusing on preparation, our complete walkthrough explains every phase from pre-test interview through to results delivery. You can also learn more about how polygraph questions are reviewed before the test.

Your Baseline Is Everything

During the pre-test phase of any polygraph examination, the examiner establishes your physiological baseline — essentially, what your body looks like at rest while answering truthful questions [5]Verified Sleep Duration and Quality in Relation to Autonomic Nervous System Measures: The Multi-Ethnic Study of Atherosclerosis (MESA)
Confirms participants sleeping fewer than 6 hours had higher baseline heart rate and greater HR reactivity to stress. Irrelevant questions are included during the actual interview in order to provide this baseline of physiological responsiveness [6]Verified The Relationship between Sleep and Autonomic Health
Confirms poor sleep quality is associated with greater skin conductance levels and lower HRV at rest. Every subsequent measurement during the actual test is compared against this baseline.

If your baseline is already elevated or unstable because of poor sleep, excessive stimulants, or acute anxiety, the margin between "normal" and "reactive" narrows considerably. Professional examiners at reputable private polygraph services will ask about your physical state before beginning. They may even postpone a test if they believe your condition would compromise the validity of the results [7]Verified Sleep deprivation: Impact on cognitive performance
Confirms total sleep deprivation impairs attention and working memory, and affects long-term memory and decision-making. Proper preparation helps you avoid that scenario.

Understanding what constitutes a polygraph baseline test is valuable context for appreciating why your physical state matters so much. There are 9 key elements that can affect the outcome of a lie detector test, and most of them are within your control during the 24 hours before your appointment.

Why Sleep Quality Directly Affects Polygraph Accuracy

Sleep deprivation is one of the most common and most impactful factors that can compromise a polygraph examination. Research in psychophysiology consistently demonstrates that insufficient sleep affects virtually every system the polygraph measures.

Cardiovascular changes: A meta-analysis of 11 randomized controlled trials involving 549 participants found that sleep deprivation impairs cardiac autonomic function, as evidenced by decreased RMSSD and increased LF/HF ratio, suggesting sympathetic predominance and vagal suppression [8]Verified Sleep deprivation effects on basic cognitive processes
Confirms 24-hour sleep deprivation had largest effect size on selective attention. Sleep-deprived individuals show elevated resting heart rate and blood pressure, along with reduced heart rate variability, making it harder for the examiner to detect the subtle cardiovascular changes associated with deception. Participants who slept fewer than 6 hours per night had higher baseline heart rate and greater heart rate reactivity to stress compared to those who slept 7 hours or more [9]Verified The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review
Confirms blue light from electronic devices suppresses melatonin secretion and influences circadian rhythm.

Electrodermal instability: Research has shown that poor sleep quality and duration are associated with greater skin conductance levels at rest [10]Verified Blue light has a dark side
Confirms Harvard research showing blue light suppressed melatonin twice as long as green light and shifted circadian rhythms by 3 hours vs. 1.5 hours. You may show spontaneous galvanic skin responses that have nothing to do with the questions being asked.

Respiratory irregularity: Fatigue often causes irregular breathing patterns, including sighing, yawning, and shallow breathing — all of which can be misinterpreted during testing.

Cognitive impairment: Total sleep deprivation impairs attention and working memory, and also affects long-term memory and decision-making [11]Verified Best Temperature for Sleep
Confirms optimal sleeping temperature of 60-67°F (15-19°C) to facilitate REM sleep stability. The pre-test interview requires you to understand questions precisely and answer them clearly, so cognitive sharpness is essential. Research confirms that 24-hour sleep deprivation had the largest effect size on selective attention [12]Verified The Effect of Deep Breathing Exercise and 4-7-8 Breathing Techniques on Anxiety and Quality of Life
Confirms 4-7-8 breathing technique was found to be beneficial in reducing anxiety levels.

Practical Sleep Recommendations

Aim for 7-8 hours of sleep the night before your appointment [13]Verified Effects of sleep deprivation and 4-7-8 breathing control on heart rate variability, blood pressure, blood glucose, and endothelial function
Confirms 4-7-8 breathing decreased heart rate and blood pressure in both control and sleep-deprived participants. Professional polygraph preparation resources consistently recommend 6-8 hours of rest before an examination [14]Verified Impact of acute ethanol intake on cardiac autonomic regulation
Confirms acute alcohol consumption results in autonomic imbalance including sinus tachycardia and reduced respiratory sinus arrhythmia. Here's how to maximize your sleep quality:

Set a firm bedtime by counting backward from your wake-up time. If you need to be up at 7:00 AM, you should be in bed by 10:30-11:00 PM to allow time to fall asleep.

Avoid screens after 9 PM. Blue light emitted by electronic devices suppresses the secretion of the hormone melatonin, which regulates the circadian rhythm and consequently influences sleep [15]Verified Exploring Alcohol Withdrawal Syndrome
Confirms alcohol cessation induces rebound stimulatory effect resulting in hyperexcitability of the nervous system. Harvard researchers found that blue light suppressed melatonin for about twice as long as green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours) [16]Verified Cardiac autonomic function during sleep: effects of alcohol dependence
Confirms chronic alcoholism is associated with cardiac and peripheral autonomic nervous system pathology. If you must use a screen, enable night mode.

Skip the late-night research. This is not the time to spend hours reading about polygraph countermeasures online. This will only increase your anxiety and is counterproductive. The examiner will address all your questions during the pre-test interview. Learn more about why you shouldn't be afraid of your polygraph test.

Create a cool, dark, quiet environment. Sleep experts recommend keeping your bedroom between 60 and 67°F (15 to 19°C) for optimal sleep quality [17]Verified The latest scoop on the health benefits of coffee
Confirms caffeine can impair sleep, cause jitteriness, anxiety, heartburn, and frequent urination. This range facilitates the stability of REM sleep [18]Verified A wake-up call on coffee
Confirms Dr. Hu's caution against caffeinated energy drinks due to high caffeine amounts. Use blackout curtains or an eye mask, and consider earplugs or white noise if your environment is noisy.

Don't take sleep aids unless prescribed. Over-the-counter sleep medications (diphenhydramine, doxylamine) can cause grogginess that persists well into the next day. If you regularly take prescribed sleep medication, continue taking it and disclose it to your examiner. Never start a new sleep aid the night before a test [19]Verified Research on Expressive Writing in Psychology: A Forty-year Bibliometric Analysis
Confirms expressive writing is beneficial for reducing anxiety based on research by Pennebaker and others.

What If You Can't Sleep?

Many people facing a polygraph the next day experience insomnia due to anticipatory anxiety. This is completely normal and expected — virtually everyone is nervous before a polygraph test, even experienced examiners [20]Verified Writing about emotions may ease stress and trauma
Confirms Pennebaker's seminal study showing expressive writing participants visited health centers less often.

If you find yourself tossing and turning, don't lie in bed staring at the ceiling for hours. Get up, sit in a dimly lit room, and do something calming for 15-20 minutes before trying again.

Practice progressive muscle relaxation: systematically tense and release each muscle group from your toes to your forehead.

Use the 4-7-8 breathing technique: inhale through your nose for 4 seconds, hold for 7, exhale through your mouth for 8 seconds. Repeat for 4 cycles. This technique, developed by Dr. Andrew Weil based on the ancient yogic practice of pranayama, activates the parasympathetic nervous system [21]Verified How to Prepare for a Lie Detector (Polygraph) Test
Professional polygraph preparation guidelines confirming caffeine, sleep, medication, and dietary recommendations. Clinical research has found that the 4-7-8 breathing technique significantly reduced state anxiety levels compared to control groups [22]Verified Effect of sleep and mood on academic performance
Confirms dehydration diminishes alertness, concentration, short-term memory, and cognitive performance. A 2022 study specifically examining the 4-7-8 technique found that it decreased heart rate and blood pressure in both control and sleep-deprived participants [23]Verified The Scientific Basis for Polygraph Testing (National Research Council)
Confirms the importance of established physiological baselines and comparison questions in polygraph methodology.

If you didn't sleep well despite your best efforts, tell your examiner at the start of the appointment. Experienced examiners encounter this regularly and will factor your condition into both the testing protocol and interpretation of results [24]Verified 80 Proposals to STOP Wrongful Convictions
Proposes universal access to polygraph examination to help prevent wrongful convictions.

The Night-Before Meal

What you eat the evening before your polygraph test matters more than most people think. The goal is to support stable blood sugar levels and comfortable digestion throughout the next day's appointment.

Eat a balanced dinner that includes a lean protein source, complex carbohydrates, and vegetables. Good options include grilled chicken or fish with rice and steamed vegetables, pasta with a light tomato-based sauce and a side salad, or a stir-fry with lean protein and brown rice.

Avoid heavy, fatty meals the night before. Large portions of fried food, rich sauces, or excessive red meat can cause digestive discomfort that persists into the next day. Extremely spicy food can cause acid reflux, stomach discomfort, and disrupted sleep. Large amounts of sugar cause blood sugar spikes and crashes that affect mood, energy, and physiological stability. Gas-producing foods in large quantities and carbonated drinks create physical discomfort during a polygraph that is distracting and can affect breathing patterns.

The Morning-Of Meal

Never skip breakfast before a polygraph test. Low blood sugar can affect the quality of data collected during the procedure [25]Verified 4-7-8 Breathing Method For Sleep and Relaxation
Confirms 4-7-8 breathing activates parasympathetic nervous system and decreases heart rate and blood pressure. Eat at least a small amount of food even if eating early isn't your usual habit [26]Verified Coffee and your blood pressure
Confirms coffee temporarily raises blood pressure in non-habitual drinkers, with habitual drinkers showing minimal effects. Low blood sugar causes irritability, difficulty concentrating, lightheadedness, and can even trigger anxiety-like symptoms.

Eat a moderate, balanced breakfast 1-2 hours before your appointment: oatmeal with fruit, eggs and toast, yogurt with granola, or a smoothie with protein and fruit. The key word is moderate — you want to feel satisfied but not stuffed. A too-full stomach can cause discomfort when the pneumograph tubes are placed around your chest and abdomen. For a deeper understanding of how these sensor components work, see our guide on the four components of a polygraph.

Hydration Guidelines

Proper hydration supports stable cardiovascular function and consistent electrodermal responses. Research has shown that dehydration diminishes alertness, concentration, and short-term memory, while rehydration can alleviate these effects [27]Verified Expressive writing as a practice against work stress: A literature review
Confirms guiding participants to formulate coherent narratives in writing positively impacts cardiac health metrics. Drink water normally throughout the evening and morning — approximately 6-8 glasses throughout the day.

Don't over-hydrate. Drinking excessive water before the test means frequent bathroom breaks, which interrupt the testing process and extend your appointment time. Stop heavy fluid intake 30-45 minutes before your appointment, and use the restroom before your session begins. Avoid diuretics — large amounts of coffee, tea, or certain herbal supplements increase urination and can lead to discomfort during the test.

Why Medication Disclosure Is Non-Negotiable

One of the most critical aspects of polygraph preparation is complete, honest disclosure of all medications and supplements you are currently taking. This is not optional, and it is not something to be embarrassed about. Every professional polygraph examiner needs this information to properly interpret your physiological data.

Cardiovascular medications: Beta-blockers (metoprolol, atenolol), calcium channel blockers, ACE inhibitors, and blood pressure medications can significantly dampen cardiovascular reactivity. An examiner must know you're taking these to properly evaluate cardio responses.

Anti-anxiety medications: Benzodiazepines (Xanax, Klonopin, Ativan, Valium) suppress the sympathetic nervous system, potentially reducing all three measurement channels. SSRI/SNRI antidepressants can also affect skin conductance. These must be disclosed, but taking unapproved substances like Xanax or beta-blockers may be flagged as attempts to influence test results.

Stimulant medications: ADHD medications like Adderall, Ritalin, and Vyvanse are sympathomimetic agents that increase heart rate, blood pressure, and electrodermal activity. Your examiner needs to know your dose and when you last took it.

Pain medications: Opioid painkillers can suppress respiratory rate and cardiovascular reactivity. Even over-the-counter pain relievers like ibuprofen should be mentioned for completeness. If the examinee is experiencing significant physical pain, the exam should be postponed, as the body's pain response will override other reactions in the charts.

Practical Medication Rules

Continue taking all prescribed medications as directed. Never skip or alter doses for a polygraph test. Stopping medication abruptly can cause withdrawal effects that are far more disruptive than the medication itself. If a medication is new, the exam ideally should not be administered until the body has become accustomed to the drug's effects, which can take a few weeks to months.

Make a complete written list of every medication, supplement, and vitamin you take, including dosages and frequency. Bring this list to your appointment. Include over-the-counter products: antihistamines, cold medications, sleep aids, melatonin, CBD products, and herbal supplements — all should be listed.

Note the last time you took each medication relative to your test time. This helps the examiner understand peak effect windows. If you have concerns about how a specific medication might affect your test, contact your examiner ahead of time. Understanding that your test results remain confidential may ease concerns about disclosing medications.

Alcohol: The 24-Hour Minimum

Avoid alcohol completely for at least 24 hours before your polygraph test, though 48 hours is better. Alcohol has well-documented effects on the autonomic nervous system. Research confirms that acute alcohol consumption results in autonomic imbalance, including an increase of sinus tachycardia and a reduction of respiratory sinus arrhythmia. Even moderate alcohol consumption the night before can have lasting effects.

Hangover effects include dehydration, elevated heart rate, headache, and cognitive fog that persist well beyond when you feel sober. Alcohol severely disrupts sleep architecture — while it may help you fall asleep initially, alcohol-induced sleep fragmentation results in more stage 1 sleep (the lightest and least restorative phase) and a rebound effect in REM sleep later in the night, contributing to vivid dreams, nightmares, and heightened autonomic activity.

After alcohol's depressant effects wear off, the sympathetic nervous system overcompensates. This represents what NIH researchers describe as a rebound stimulatory effect, resulting in hyperexcitability of the nervous system. The sympathetic rebound leads to heightened anxiety, sweating, and elevated blood pressure — all of which contaminate polygraph readings. Chronic alcoholism is associated with the development of cardiac and peripheral autonomic nervous system pathology, and even moderate alcohol effects on autonomic function can persist.

Some people mistakenly believe that having a drink or two will calm their nerves before a test. This is counterproductive — experienced examiners will not test individuals who are intoxicated or under the influence.

Caffeine: One Cup Is Fine, More Is Not

If you are a regular coffee or tea drinker, having one standard cup (8 oz of regular coffee or equivalent) in the morning is acceptable and even recommended. Professional polygraph examiners advise maintaining your normal routine — do not drink more caffeine than you would normally drink before the exam. Abruptly cutting out caffeine when you normally drink it can cause withdrawal symptoms — headache, irritability, difficulty concentrating — that are worse for your test than the caffeine itself.

However, limit yourself to that single serving. Caffeine can impair sleep, cause a jittery feeling, and even cause anxiety, along with heartburn, frequent urination, and palpitations. While moderate coffee consumption does not appear to increase the risk of serious cardiovascular problems in healthy people, it may temporarily raise blood pressure. For a deep dive into the science, read our guide on whether caffeine can affect polygraph test results.

Avoid energy drinks entirely. Products like Red Bull, Monster, and pre-workout supplements contain caffeine levels equivalent to 2-5 cups of coffee, often combined with taurine, guarana, and other stimulants. Harvard's Dr. Frank Hu cautions against caffeinated energy drinks, noting that high caffeine amounts have sent drinkers to the emergency room.

Recreational Drugs and Cannabis

All recreational substances should be avoided before a polygraph test. Cannabis/marijuana affects cardiovascular function for hours after use and may still influence your system the next morning. CBD products, while less psychoactive, should also be disclosed to your examiner. Experienced polygraph examiners will not test individuals who are under the influence — using marijuana or alcohol before your scheduled exam will result in you being sent home.

If you're a regular smoker or vaper, don't try to quit the morning of your test. Nicotine withdrawal increases heart rate, irritability, and anxiety. Stimulants such as caffeine and nicotine can increase anxiety and affect physiological responses. Have your normal amount but avoid smoking immediately before the appointment, as acute nicotine intake spikes cardiovascular activity.

All other substances — cocaine, amphetamines, MDMA, and similar drugs — cause profound sympathomimetic effects that persist well beyond the subjective high and will compromise any polygraph examination. For context on how substances interact with polygraph testing, see our article on what can cause a false positive on a polygraph.

Understanding the Sensor Placement

Your clothing choice matters because of where the polygraph sensors are physically placed on your body. During a standard polygraph examination, the following components are attached:

Two pneumograph tubes (thoracic and abdominal) are placed around your chest and abdomen to measure breathing patterns. These go over your clothing. Two stretchy cords will be placed to record breathing — one above your heart and one below.

A cardio cuff (similar to a blood pressure cuff) is placed on your upper arm to measure relative blood pressure and pulse rate.

Finger plates or GSR electrodes are attached to two fingers on one hand to measure electrodermal (sweat gland) activity. Sometimes two sticky sensors are placed on the palm of your hand.

A motion sensor pad is typically placed on the seat of your chair to detect significant movement. For more detail on the sensor components, read our guide to the four components of a polygraph.

Clothing Recommendations

Wear a comfortable, loose-fitting top. A t-shirt, blouse, or lightweight sweater works well. The pneumograph tubes need to be placed around your torso, and tight clothing can interfere with accurate respiration measurements. Avoid thick, bulky sweaters or jackets that add layers between the tubes and your body.

Choose short or easily rolled sleeves. The cardio cuff goes on your upper arm, typically the left. Wear a short-sleeved shirt or one with sleeves that can be easily pushed above your bicep.

Dress in layers. Testing rooms can be cool (to help control sweating variables) or warm depending on the location. A light cardigan over a t-shirt is ideal.

Wear comfortable pants or a skirt. You'll be seated for an extended period — polygraph examinations typically take two to three hours. Avoid clothing with restrictive waistbands, belts, or buttons that dig into your abdomen.

Remove jewelry and watches before the test. Rings on the fingers where GSR electrodes will be placed need to be removed. Leave heavy bracelets, watches, and rings at home.

What Not to Wear

Body-shaping undergarments — Spanx, compression garments, or tight sports bras restrict torso movement and interfere with pneumograph readings.

Heavy coats or multiple thick layers — these must be removed anyway and create unnecessary hassle.

Strong perfume or cologne — testing rooms are small and enclosed. Strong fragrances can be distracting to both you and the examiner and may trigger headaches during the lengthy session.

Clothing that makes you self-conscious — if you're constantly adjusting your outfit, you're distracted. Wear something you feel comfortable and confident in. While what you wear doesn't directly affect the results, it can send a message about how seriously you take the exam.

Understanding That Anxiety Is Normal

Virtually everyone is nervous before a polygraph test. This is true regardless of whether you have something to hide. With over 22 years of experience, one advanced board-certified expert polygraph examiner noted that he experienced nervousness every time he took a polygraph test himself, confirming this feeling is normal even for seasoned professionals.

Professional polygraph examiners know this and are trained to distinguish between general nervousness and the specific physiological reactions associated with deception. Your well-trained experienced examiner will be able to observe the emotions you display and should be able to relieve your anxiety during the pre-test interview. If you're taking a private test to clear your name from false allegations or to resolve trust issues in a relationship, remember that your honesty is your greatest asset.

Research on the neuroscience of deception has shown that the left dorsolateral prefrontal cortex (DLPFC) is more activated during lie preparation than truth preparation, demonstrating that deception requires additional cognitive effort that truthful responding does not. This means being truthful is actually the more natural, lower-effort state — which works in your favor.

Effective Anxiety Management Techniques

Breathing exercises are one of the most effective tools for managing pre-test anxiety. The 4-7-8 breathing technique can play a significant role in activating the parasympathetic nervous system and helping you shift toward tranquility. Slow breathing reduces oxygen consumption, heart rate, and blood pressure while increasing parasympathetic tone and improving sympathovagal balance.

Write down your worries the night before. Decades of research by Dr. James Pennebaker at the University of Texas at Austin has demonstrated that expressive writing — writing about one's deepest thoughts and feelings — is beneficial for reducing anxiety. In his seminal 1986 study, participants who wrote about traumatic events for 15 minutes over four days visited the campus health center less often in the following six months. Writing helps people organize thoughts, and forming a coherent narrative has been shown to positively impact cardiac health, with participants showing significantly lower average heart rates and higher heart rate variability.

Visualize a successful outcome. Spend a few minutes the evening before picturing yourself sitting calmly in the examination room, answering questions honestly and clearly, and walking out with accurate results.

For more comprehensive guidance on managing test anxiety, read our dedicated article: Should I be nervous about my polygraph test?

Essential Items Checklist

Ensure you have all required documentation with you on the day of the test — having everything in order can help reduce stress and ensure a smooth process.

Government-issued photo ID (driver's license, passport, or state ID).

Your booking confirmation or appointment reference number.

A written list of all medications, supplements, and vitamins you currently take, including dosages.

Any documents your examiner specifically requested — this may include case-relevant materials, background information forms, or legal correspondence.

A light snack and water bottle (for after the test, especially if your appointment runs long).

Reading glasses if needed — you may need to review and sign consent forms or read test questions.

Leave your phone on silent and be prepared to turn it off during the examination. The examiner will undoubtedly request that cell phones be silenced.

3-2 Hours Before Your Appointment

Eat a moderate breakfast. Maintain your normal routine — drink your usual coffee, eat breakfast as you normally would. Take all prescribed medications as directed by your physician.

Review your medication list and make sure it's complete. Double-check that you have your ID, confirmation, and any requested documents.

1 Hour Before Your Appointment

Stop heavy fluid intake. Use the restroom before leaving for your appointment.

Get dressed in your pre-selected comfortable outfit. Do a final check: no heavy jewelry, no strong fragrance, comfortable shoes.

If you're a smoker, have your normal cigarette but avoid smoking in the 30 minutes immediately before the appointment.

Do a brief 4-7-8 breathing exercise — 4 cycles of inhaling for 4 counts, holding for 7, exhaling for 8.

30 Minutes Before: Arrival and Settling In

Arrive 10-15 minutes early. Rushing raises heart rate and blood pressure before the test even begins. Plan your route in advance and account for traffic or parking.

When you arrive, take a moment to sit quietly and continue calm breathing. Remind yourself that the examiner's job is to get accurate results, not to intimidate you.

A consent to polygraph examination and waiver of liability will be presented and reviewed for you to sign. Read it carefully and ask any questions you have before the examination begins.

Top 10 Pre-Test Errors

Researching countermeasures online. Spending hours reading about polygraph-beating techniques increases anxiety and is counterproductive. Many people say these websites increased their anxiety significantly. Worse, attempting any countermeasures during the test may cause the examiner to immediately fail you. Learn why science says you probably can't deceive polygraph testing.

Skipping meals. Low blood sugar causes irritability, difficulty concentrating, and physiological instability.

Drinking alcohol to calm nerves. Even moderate alcohol consumption creates lasting autonomic nervous system effects that contaminate readings.

Over-caffeinating. More than your usual single cup elevates heart rate, blood pressure, and electrodermal activity.

Taking unprescribed medications. Never take a sedative, beta-blocker, or any other medication not prescribed to you before a polygraph.

Wearing uncomfortable clothing. Tight clothing interferes with pneumograph readings and creates distracting physical discomfort.

Arriving late. Rushing creates physiological arousal that takes significant time to subside.

Failing to disclose medications. This can lead to misinterpretation of your physiological data.

Staying up all night worrying. Even a rough night is manageable if you tell your examiner, but deliberate sleep deprivation is not.

Not using the restroom before the test. Physical discomfort during a polygraph is distracting and can affect breathing patterns.