Forensic analysis may be able to help convict a guilty party, but one of its weaknesses is that the whole process would take a lot of time. From the analysing of blood and fingerprints to the whole crime scene inspection and reconstruction, it will definitely take a long time to complete the process. This will extend the date of the verdict to be announced, which will incurs additional costs. Also, as the whole process takes a very long time, there is a possibility that the evidence collected may wear out or expire, leading to inaccurate results, affecting the outcome of the verdict.

Evidence is prone to manipulation, which may result in a wrongful conviction

The purpose of Forensic Analysis is to collect and analyse the evidence in a crime scene to gather results of what has been left over at the crime scene. The analysis is able to give the investigators an insight of what really happened when the crime was committed. However, what if these evidence have actually been planted by the criminals themselves? What if the evidence were meant to purposely lead the investigators to the wrong path of investigation? Evidence are not constant objects that will always show the truth. They can be changed and manipulated to the point that these evidence will be able to implicate an innocent person, leading to a case of wrongful conviction and allowing the criminal to escape scot-free.

Evidence can be well hidden and it is difficult to distinguish between relevant evidence and non-relevant evidence

In a crime scene, there is definitely evidence present. But the problem is distinguising which evidence is useful and which evidence is not relevant. Before distinguishing which is the most impactful evidence that is able to make a conviction, forensic investigators need to analyse the large amount of evidence found at the crime scene. Forensic investigators know that the main piece of evidence is hidden somewhere in the clump of evidence, but unless they analyse the whole clump of evidence, they will not be able to find the main piece of evidence

Misconceptions and ignorance in the forensics field can mislead the investigation

Forensic Science encompasses a very wide scope of science and technology and there is much more knowledge that we have not yet uncovered. Innocent people may be convicted based on wrong evidence due to current gaps in our understanding of technology.
 

One example is the October 2012 Adam Scott rape case where he spent five months in prison due to a forensic mix-up meant that he was falsely accused of rape.