How Do the Police Investigate Crimes?

When police officers arrive at a crime scene, they may be lucky in that the perpetrator is still on the premises. In that case, the police can arrest the person on the spot and focus on building a case against them that will stand up in court. But what about crimes where the criminal is no longer at the crime scene? How do the police investigate and solve those crimes?

Some tools that police use when investigating a crime are interviews and interrogations. Police will also collect any physical evidence left at the scene of the crime and evidence referred to in an interview or interrogation. They then use the information and evidence to piece together a police report of the crime. In order for a criminal charge to stick, the police must have evidence that supports their final report.

So, how do law enforcement officials investigate crimes? Read on to learn more about the basic investigation steps that police use to build a criminal case.

Police Investigations: The Crime Scene

As soon as the police receive a phone call about a crime, they send law enforcement officers to the scene. The officers might catch the alleged criminal right on the scene. The officers will then arrest this person and take them to the police station for booking.

Even if the police catch the person red-handed, they will still need to collect enough evidence at the scene of the crime to support a criminal charge. This evidence collection will include interviewing the potential witnesses at the scene. The police will also conduct a site investigation. This includes taking photos, measurements, and objects at the scene of the crime.

At all times, the police department and its employees must obey the U.S. Constitution's Fourth Amendment on permissible search and seizure. If the police wish to search any private property, they must first get a search warrant or have probable cause that would allow a search without a warrant. Private property can include one's home or private space and one's personal belongings, such as a purse or electronic device.

Police Investigations: Interviewing Witnesses

When police officers conduct interviews, they're looking to establish the facts of the case. Often, they'll interview witnesses separately. This ensures that the police have each witness's individual recollection of the events.

The police will want to talk to people who have personal knowledge of the crime or the alleged perpetrator. This includes family members or witnesses to the crime. To have personal knowledge, the witness must have seen, heard, smelled, tasted, or touched something related to the crime. The police will document witness statements along with their own observations. This information will be available to future police officers, detectives, and prosecutors.

Police Investigations: Law Enforcement Observations

A key component of any criminal investigation is the observations of the police officers. Police officers learn to observe and notice details. They will note the position of weapons, blood stains, clothing, and any other details that might explain the criminal offense.

Police Investigations: Physical and Forensic Evidence

The police will also collect physical evidence at the crime scene. Police must record and document each bit of evidence pursuant to criminal law. Police collect physical items by using gloves to preserve fingerprints and limit contamination. They gather forensic evidence, like fingerprints, blood, or saliva, and send it to labs for analysis.

The police will then place the physical evidence in a marked special bag so it can be identified later. Police will also look at electronic evidence like cell phone data, online searches, and communications.

Police document the chain of custody for each piece of evidence. This establishes an unbroken chain of custody from the time of collection to presentation at trial. This helps ensure nobody has tampered with evidence.

Police Investigations: Custodial Interrogations

During a criminal investigation, the police will interrogate a list of suspects. From the questioning, the police hope to get a confession. Many times, police record these interrogations and witness interviews by video or audio for documentation.

Police officers and detectives are skilled interrogators. They have studied human behavior and body language. Interrogation is a science. Detectives know how to gain a suspect's trust and how to manipulate them into a confession. But the police cannot violate a person's Miranda rights and Constitutional rights to get a confession.

What Happens When the Police Complete Their Investigation?

Once the police complete their criminal investigation, they will present the findings to the district attorney's office. The district attorney's office will then decide whether the case is strong enough to bring to court. Depending on the seriousness of the crime, the prosecution will then decide whether the case should go to a grand jury or a preliminary hearing. The grand jury process is only required for certain felony offenses and is not required for misdemeanor charges.

If the case goes to a grand jury, the grand jury will decide whether there is enough evidence to prove that the suspect committed a crime beyond a reasonable doubt. If the grand jury finds that there is enough evidence to bring criminal charges, there will be an arraignment. During an arraignment, the judge reads the charges to the criminal suspect. The court will then ask the suspect to enter a “guilty" or “not guilty" plea.

Want to Learn More About How the Police Investigate Crimes? Talk to a Criminal Defense Lawyer

Police investigations are an important part of the criminal justice system. But law enforcement agencies can make mistakes. These mistakes sometimes result in an innocent person going to prison. There are many legal guidelines that police officers must follow when investigating crimes. It is especially important to know when an officer must have an arrest warrant or search warrant.

If you're the subject of a police investigation, you should speak to an experienced criminal defense attorney. An attorney can ensure that your rights are protected and can provide you with sound legal advice during the criminal justice process.

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