Top 7 Police Mistakes in Criminal Investigations

This post is going to explain seven (7) minor to serious mistakes police can make when conducting a criminal investigation.

In fact;

These are the same mistakes I analyze when conducting my own criminal investigations for clients.

These mistakes will usually involve the following:

  • Violation of suspects rights
  • Breach of procedure regarding evidence

Lets review the mistakes….

Conducting a Search, Stop or Arrest Without a Warrant, Consent or Probable Cause

Before a police officer can stop, search or arrest you, he or she must have the following:

  • Reasonable suspicion to stop you, or
  • Probable cause to search or arrest you, or
  • Consent to search. or
  • A warrant to arrest or search you.

What is a “Terry Search?”

A Terry search is based on reasonable suspicion, a variant to probable cause and a lesser standard.

If police saw you in the midst of a street transaction with known drug dealers, or saw you running from a store holding unpackaged items in your hand, this would likely generate reasonable suspicion and justify a stop.

What is Probable Cause?

This is defined in various ways, but it is essentially “an honest and strong suspicion or a state of facts that would cause a prudent person to believe that a suspect committed the crime under investigation”1.

Police cannot stop you because you look suspicious or are of a particular color, race or ethnic origin.

Absent Consent

Police can search you if you consent and officers will often testify that a defendant gave consent for police to search their car, office, or home2.

Otherwise, a valid search warrant can only be obtained based on:

  • A sworn, detailed affidavit by a police officer before a neutral magistrate or judge
  • Probable cause that a crime has been committed
  • Language that describes with reasonable particularity the place to be searched and the items or person to be seized
  • And served within normal business hours (7 am and 10 pm) although a judge can authorize it at any time of day or night for good cause
Other mistakes police make when wanting to make an arrest or search include:
  1. Fabricating or exaggerating facts to find probable cause to issue the warrant
  2. Not being specific in the items to be seized
  3. Searching for items not within the scope of the warrant
  4. Seizing items not within the scope of the warrant
  5. Serving the warrant outside the hours of its scope
  6. Serving the wrong person or at the wrong location

Absent An Arrest Warrant

In the absence of an arrest warrant, police cannot arrest a person unless the officer has reasonable cause to believe that person has committed a crime.

Can You Be Arrested In Your Home Without A Warrant?

Arrests within a person’s home are not permitted without a warrant, even upon probable cause, unless there are exigent circumstances3.

This extends to persons arrested in someone else’s residence4.

What Are Exigent Circumstances?

Exigent circumstances refers to emergency situations that require immediate action to prevent imminent danger to life or serious damage to property, or to prevent or forestall the imminent escape of a suspect or destruction of evidence5.


Although the court essentially relies on the officer’s discretion to decide whether there are exigent circumstances to justify an arrest in a dwelling without a warrant, the court does look to certain facts that existed at the time of the arrest6:

What Facts Does The Court Review?

  • A grave offense is involved (physical violence)
  • Suspect is believed to be armed
  • There is a clear showing of probable cause
  • There exists a strong showing that the suspect is on the premises
  • There is a strong likelihood the suspect will escape if not immediately apprehended
  • The entry is made peaceably, even though no consent was given to enter

What Errors Do Police Make With Warrants?

Errors by police occur when they are unable to make a credible showing that the defendant was either on the premises or was armed, or that he or she would escape if not placed under arrest.

If consent was not given, officers may not use force to enter and arrest the suspect without a warrant.

If a court deems the arrest unlawful, all charges stemming from that arrest may be dismissed.

Neglecting to Read Arrestees Their Miranda Rights

Miranda rights are those concerning a defendant’s right against self-incrimination and to have the assistance of counsel when being questioned or interrogated by police7.

Your Miranda rights must be read to you before the police question you and you are in custody8 or your statements are inadmissible unless you provide them willingly.

Watch this video to understand when miranda comes into play.

What Are Your Miranda Rights?

  • Your have the right to remain silent.
  • Anything you say can be used against you in a court of law.
  • Your right to consult with an attorney and have that attorney present with you during questioning.
  • If you cannot afford an attorney, the court will appoint one for you.

What Mistakes Can Police Make Regarding Miranda Warnings?

Police officers may place you in custody and not immediately provide you with the Miranda warning. You are considered in custody if:

  • Police place you in handcuffs
  • You are Placed in a locked room
  • You have asked and been told you are not free to leave yet
  • Your freedom of action is restricted in a significant way
You are considered under arrest once you are in custody or are not free to leave, even if the police have not said anything to you about being under arrest.
Interogation Of Minors

If a minor has been arrested or taken into custody, then California law requires that police read the minor his or her Miranda rights, regardless of whether they intend to interrogate the defendant.

If the minor’s request for a lawyer or parent to be present was denied and then made an incriminating statement, the court will look at the overall circumstances to determine if the statement was given voluntarily.

What If A Minor Was Not Read The Miranda Warning?

If the child is not read the Miranda warnings and gives an incriminating statement, courts will examine the overall circumstances to determine if the child was aware that he or she was free to leave.

The age of the minor is an important consideration since a child may not fully understand that he or she is free to not answer questions9.

Asserting Right to Counsel

Generally, if the defendant states that he wants to assert his right to counsel, then officers may not re-approach the defendant and attempt to question him or her unless the attorney is present when the defendant waives his or her right to remain silent.

What If The Officer Returns Later That Day?

Even if the officer returns a few hours later or the next day, repeats the Miranda rights to the defendant, and the defendant makes incriminating statements, these cannot be used as evidence unless the defendant unequivocally and voluntarily waives those rights.10.

For example, if the defendant happens to re-initiate the interrogation, regardless if he advised the officers that he wished to remain silent or wanted to speak to an attorney, then the officer must re-advise the defendant of his Miranda rights and seek a waiver11.

Coercion and Involuntary Statements

An involuntary statement or one coerced by police occurs when the defendant’s free will has been overcome12. Your free will may be compromised if you are in intense pain and an officer persists in questioning you.

But there are other less obvious situations which a court could interpret as being intimidating and coercive enough in determining that your free will was overcome when you made an incriminating statement. This can occur even if you have been read your Miranda rights and waived them.

Factors that courts review if coercion is alleged in obtaining a statement include:

  1. Length of the interrogation
  2. The defendant’s age, maturity or mental health
  3. Promises of leniency
  4. Depriving you of food, water or bathroom use
  5. Interrogating you at gunpoint
  6. Striking you and threatening more physical harm
  7. Threats of no food, bathroom breaks, sleep, or that harm will come to an intimate partner
  8. Possibly questioning you while you are heavily intoxicated or under the influence of drugs so long as you were unable to think clearly
  9. Continuing to question you after you have asserted your rights

If Police Officers Lie To You Is That Coercion?

Lying to you that evidence has been found to convict you is not considered coercion13.

Getting you to talk while lying about not having the discussion recorded is not deception in forcing you to answer questions14.

Writing a Bare Bones Police Report and Leaving Out Important Details

A police report that leaves out important details can come back to haunt the officer and can hinder a successful prosecution.

What Information Is Included In The Police Report?

Police reports contain relevant information about:

  • The officer’s observations while investigating a case
  • Evidence found at the scene.
  • Witness’ statements
  • Chain of evidence

Officers also rely on the police report when testifying at preliminary hearings, motions, or at trials since it may be weeks or months since the event and arrest took place.

What Important Information Could Be Missing From A Police Report?

A report with the bare minimum of facts and observations can be used by the defense to question or point out the lack of certain important information:

  • Weather conditions at the time
  • Description of the vehicles, firearm, drugs or other contraband
  • Where the witness was situated when the offense was observed
  • The content of witness statements
  • The demeanor of the defendant
  • Who else was present at the scene
  • Where certain evidence was found and its condition
  • Who had access to the evidence
  • Who had access to the crime scene
  • How was the crime scene secured
  • That certain allegations made against the defendant are not in the report

How Can a Defense Attorney Use This To Their Advantage?

If a police report lacks essential facts, then the defense attorney can suggest that certain facts not included may have been exculpatory or suggestive of the defendant’s innocence or that events may or may not have occurred as alleged since there is no record of it.

Juries will often not tolerate shoddy police work or practices and may feel that an officer is hiding something. Since a criminal conviction requires unanimity in finding a defendant guilty, only one juror needs to find reasonable doubt.

Not Interviewing And/Or Obtaining Contact Information For Percipient Witnesses

Officers sometimes fail to find or to interview percipient witnesses who are known to them and whose statements could support other evidence or which could exonerate a defendant

What are Percipient Witnesses?

Percipient witnesses are those persons who directly observed an event such as having seen the defendant at the scene of the crime or someone who can provide some exculpatory evidence that helps the defense.

Memories Fade

How Does This Police Mistake Affect A Case?

Memories or observations of events vary widely among witnesses to the same event and are known to fade over time, or be influenced by news accounts or statements by other witnesses or observers.

By interviewing a witness at the scene, an officer can preserve these memories of the event without these influences. If the witness is needed at a future time but is unable to recall certain facts, the previous statement can be used to refresh the witness’ recollection.

If contact information for the witness is not obtained, it is probable that if the matter goes to trial, an essential witness cannot be found and the charges may have to be dropped.

Not Booking Important Evidence Items Into Evidence

Police may fail to book certain evidence, either because of a mistake or because they didn’t believe the evidence was relevant to the case.

In rare circumstances, police officers may intentionally fail to book important items into evidence, however the more likely scenario is that they overlooked a crucial item in some way.

Are Police Officers Required to Follow Certain Procedures with Regard to Evidence?

Evidence that is found at the crime scene or elsewhere that is relevant to the case is required to be booked into evidence so that it may be preserved and remain untainted.

Once booked, it is also subject to being disclosed to the defendant’s attorney.

Evidence may include
  • Items used in the commission of a crime (weapons or vehicles)
  • Items that are the subject of a crime such as contraband
  • DNA evidence
  • Body-worn camera recordings
  • Photographs
  • Recordings of statements taken or obtained by others
  • Identity of witnesses
  • Witness statements
  • Blood test results
  • Breath sample results
  • Documents purported as incriminating or that could be exculpatory in nature
  • Objects at scene that may identify or lead to another suspect

A police shooting of an unarmed suspect whom the officer claims attacked the officer with what appeared to be a weapon. Body-cam recordings that were not booked into evidence reveal that the suspect had his hands up and was willing to be taken into custody.

If such evidence was available and known to police and not booked into evidence, but was later discovered, the defendant’s conviction could be dismissed.

Not Following Proper Police Procedures to Ensure Chain of Custody

Whenever a unique or important piece of evidence is found such as a firearm, blood or DNA sample, the police must follow proper procedures in what is referred to as a “chain of evidence.”

What is the Chain of Evidence?

The chain of evidence is what must be proved in a court of law to show what happened to the evidence from the time it was found to the point where it is introduced into evidence at the trial.

The prosecution has the burden of proving chain of evidence.

What Procedures Must The Police Follow With The Chain of Evidence?

  • The item or evidence is what it purports to be (blood or DNA sample from the defendant; bullet from the gun used in the crime)
  • Who has possessed the item or evidence since it was taken from the scene or defendant
  • That it has been in constant possession of the police or other agency authorized to handle it
  • That the he evidence has remained in substantially the same condition from the time the person within the chain of custody took possession of it until it was transferred to another person or that it was in a secure storage area
  • The item was marked according to procedure and properly identified
Not Making a Clear Record of Items Seized or Where Said Items Were Taken

Police are trained to carefully make a record of all evidence seized that includes where the evidence was taken. This constitutes the initiation or beginning of the chain of custody that must be documented up until the time the evidence is introduced.

Mistakes That officers Make During Investigations

Officers err when they either fail to make the record at the earliest opportunity or do make a record days or weeks later and must rely on faulty recollection. If several items were taken, the officer must describe each item and the area where it was found.

Photos of the scene or testimony from other officers at the scene may conflict with the record made. If so, there exists a discrepancy or break in the chain of custody.

Break in the Chain of Custody

What Happens if there is a Break in the Chain of Custody?

When a vital link in the chain of custody is broken or unaccounted for, the judge has a duty to exclude the evidence15.


A police officer may have found a bloody glove at the scene and placed it in a plastic bag.

However, the officer cannot state exactly where the glove was found, He may also be unable to state  to whom he gave the bag with the glove to after securing it. Or, the bag was left on top of a police vehicle and not placed in a secure locker so that multiple people had access to it.

Prosecutor Must Show that it is Reasonably Certain the Evidence was not Altered.

If the procession of who had possession of the evidence and what was done to it cannot be shown, it is likely a judge will rule it inadmissible as it cannot be offered as it purports to be.

A prosecutor has the burden when offering a piece of evidence of showing that it is “reasonably certain” that the evidence has not been altered16.

Suppression of Evidence

What Should a Defense Attorney do When the Chain of Custody is Broken?

When an officer that is in charge of

  • Recovering the evidence,
  • Securing the evidence,
  • Marking and identifying the evidence, and
  • Ensuring that it is not altered

Fails to show that each link in the chain of possession is accounted for, then that evidence may be suppressed.

Although a trial court has some discretion in determining if the break in the chain was material or vital. If it is just as likely as not that the evidence analyzed was not the evidence originally received, then the court must exclude it17.

Escalating a Situation by Use of Force

If excessive force is alleged, police misconduct may lead to the prosecution offering a reduction in charges but this will not necessarily require a court to dismiss charges.

Instead, a defendant may bring a civil law suit against the police for wrongful death and/or federal civil rights violations under U.S.C. Title 42, Section 1983.

It can also lead to criminal charges against the police for:

How Courts Approach Excessive Force

The seminal case in excessive use of force by police is Graham v. Connor (1989) 490 U.S. 386, wherein the court described how a court should approach the issue by making the following inquiry:

  1. What was the severity of the crime the officer was investigating?
  2. Whether the suspect presented an immediate threat to the safety of the officers or the public
  3. Whether the suspect was actively resisting arrest or attempting to escape

If the officer was aware of the suspect’s history of violence, mental illness or impairment due to drugs or alcohol, this is a vital factor in the officer having to resort to force18.

Civil Suit

However, police can easily misjudge a situation and escalate matters by resorting to excessive force when other means of effectuating the arrest could have been used.

A Civil Suit Against Police May Assert:

  • The use of force was disproportional to the person’s resistance
  • There was no urgent need to resolve the situation
  • The officer could have used less force and still accomplished the objective
  • The officer lacked training and competency in using the tools of force that were applied
  • The officer’s conduct was not objectively reasonable
  • The officer initiated the force

Get Legal Help

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  1. Beck v. Ohio (1964) 379 U.S. 89, 91 []
  2. Schneckloth v. Bustamonte (1973) 412 U.S. 218, 291 []
  3. People v. Campa (1984) 36 Cal.3d 263, 27-277 []
  4. People v. Tillery (1979) 99 Cal.App. 3d 975, 978-979 []
  5. People v. Ramey (1976) 16 Cal.3d 263 []
  6. Dorman v. U.S. (D.C. Circuit 1970) 435 F.2d 385 []
  7. Miranda v. Arizona (1966) 384 U.S. 436 []
  8. California v. Beheler (1983) 463 U.S. 1121 []
  9. J.D.B. v. North Carolina (2011) 564 U.S. 261 []
  10. Edwards v. Arizona (1981) 451 U.S. 477 []
  11. Oregon v. Bradshaw (1983) 462 U.S. 1039 []
  12. Rogers v. Richmond (1961) 365 U.S. 534, 540 []
  13. People v. Farnham (2002) 28 Cal.4th 107; Oregon v. Mathieson (1977) 429 U.S. 492 []
  14. People v. Sims (1993) 5 Cal.4th 405 []
  15. People v. Lucas (1995) 12 Cal.4th 415, 444 []
  16. People v. Catlin (2001) 26 Cal.4th 81, 134; People v. Herrera (2000) 83 Cal.App.4th 46, 61 []
  17. People v. Williams (1997) 16 Cal.4th 153, 196; People v. Jimenez (2008) 165 Cal.App.4th 75 []
  18. Krueger v. Fuhr (1993) 991 F.2d 435 []


In regards to a possession
misdmeanor charge. Then failure to appear, ending in a $2500 bench warrant, what should the next step taken by the person with a $2500 Bench Warrant?

Hi John: The next step would be to go to the courthouse from where the warrant was issued and ask the court to recall the warrant. I recommend being represented by counsel for that purpose.

Can a officer stop you traffic stop but he’s on foot investigating another crime and instead of him pulling u over behind the wheel of his car I had gotten out the car and walked towards him can he right a ticket for driving without license

I was pulled over for speeding in seattle on new years eve. Thankfully the officer pulled me over in front of my moms place. I let the 3 children go inside my mothers so i could have a cigarette and talk to the officer. I gave the officer my information and asked my girlfriend for a cigarette as she is packing the cigarette pack the officer tells me that i am not smoking during a traffic stop. I lightly chuckled and asked if that was a new law that i had yet to hear of and he says no I am telling you that you are not going to smoke a cigarette during a traffic stop. I said you dont understand officer i have been driving for hours with 3 young kids on new uears eve so i am smoking the cigarette the moment you walk away to check my information. We go back and forth saying no and yes. My girlfriend handed me a cigarette and started recording on her phone. The officer turns and takes a step towards his patrol car and i light the cigarette he immediately turns towards me and yells I SAID NO and uppercut/ choke hold type maneuver on my throat the lit cigarette lands on one of the kids blankets that they brought the officer reaches over me grabs the cigarette throws it then tells me get out of the car. Back up arrives and they give me all these test that i had never taken before or heard of. The officer giving me the test says i passed all the test i am fine and they had to test me because i seem on edge. I told him his partner hit me of course im on edge he then tells me that if i had kept my mouth shut in the first place that none of this would have happened. The officer that pulled me over said that everything was being recorded and my girlfriend sent me the video. I sent it to a couple attorneys and neither of them have any advise or recommendations for me. Can you recommend an attorney? My video only shows the assault and me taking a seat on the bumper of the police car. No charges or tickets resulted from this event. I did have dental problems afterwards and had to have an emergency surgery to remove a lower tooth during the stay at home order. I am sure everyone has heard of the seattle east precinct that now has a concrete barricade around it. Needless to say the pandemic and protests make it difficult to do much of anything here in Seattle and i would like something done about this because it should never have happened all he had to do was walk back to his car. I had cooperated and gave him the documents he asked for and he could see that it was a brand new pack of cigarettes oh thats right he claimed that there could have been contaminated with fentanyl!!! I am sure the cigarette manufacturers are contaminating their products with fentanyl. The pack still had the cellophane on it and then for his buddy blaming me for exercising my 1st amendment right and asking if it was a new law. I was serious it wouldnt surprise me if it were a law but its not and i did nothing wrong that evening all i was doing was chaperoning 3 kids to see the fireworks at the space needle because none of them had ever seen them before. You can hear my mom in the video freaking out because the police presence over this matter made her believe that they were there to execute me. I did not fight back or call the officer any names i was never placed in handcuffs. I tried my best to stay calm obviously i was agitated and wanted to kick the officers ass but he had a gun and back up oh i feel like no one is taking this case because i am white. My bestfriend is black and was tackled by seattle pd for jaywalking a couple years earlier and he believes that it is because i am white that no lawyer will take the case. I just want the officers held accountable and for tue police department to pay for my upcoming dental surgeries because i dont think my Obamacare is going to cover anything but the extraction of several teeth. I have had atleast 3 teeth crack and had an abscess tooth that during the pandemic no dentist could touch because it wasnt considered life threatening at the time. I had to go to the E.R. 3 days in a row for antibiotic saleen drips just to get the swelling to go down and relieve the pressure and the pain. I refused all narcotic medications because i dont want to be addicted to them

Hello Julian: I recommend going to the website of the National Association of Criminal Defense Lawyers and searching for an attorney in Seattle.

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