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Physical evidence is direct objective evidence that can provide important information in a case, such as criminal tools and items, etc. It is very important in solving cases and convicting people. Similarly, if one step is wrong, the next step is wrong, so physical evidence is the most difficult.

Investigators in the Urumqi fire case (2014) were successful in tracking the source of the fire and uncovering the arsonist's method and intentions by gathering tangible evidence left at the fire site, such as burn trails and debris.

The preservation of the crime scene helps to guarantee the evidence's integrity and trustworthiness, keeps it from being contaminated or damaged, offers a clear image of the scene for the investigation, and reduces later legal challenges.

The Case of the White Assassin in the Dark (1994), in which rigorous scene protection permitted successful DNA extraction, exposing the identify of the perpetrator.

In instances involving personal injury or death, forensic science is crucial in providing expert cause-of-death analysis and biological evidence to offer a scientific foundation for deciding blame.

The Robert Picton Serial Killer Case (2002), in which modern forensic scientific investigation assisted police in confirming the defendant's guilt.

Fingerprints are widely used as a useful tool in criminal investigations because they have distinctive physical characteristics and, like leaves, are unique to each individual, are often used to identify criminals, and are a solid piece of evidence for a court of law.

The Van Buren serial murder case (2002), in which the suspect's fingerprints were discovered at the crime site and were crucial in his conviction.

Ballistic testing is important for solving gun crimes because it analyzes ballistic characteristics and links the gun to the crime scene and to the black or legal gun possessed by the offender, for the purpose of identifying the murder weapon and solving the crime.

Ballistics testing showed the characteristics of the killer's weapon in the Montreal Polytechnic University shooting (1989), providing significant evidence to solve the case.

DNA testing is a very accurate means of personal identification and can be used to link a suspect to the scene of a crime, but there are very few things the dna doesn't match up to, such as the offender having had a previous bone marrow transplant, providing corroborating evidence, and the court recognizes this.

In the case of the twenty-nine persons arrested in Urumqi (2015), DNA testing aided in identifying many suspects and establishing the gang's criminal network.

Indentation analysis is utilized for individual identification, such as footprints and tire tracks, and it aids in tracking suspect activity and providing important information about the crime scene.

In the Nanjing Postal Robbery case (2010), imprint analysis revealed the traces left by the robbery criminals at the crime scene, which provided strong clues for solving the case.