Effective police investigation plays a crucial role in ensuring justice, maintaining law and order, and successfully prosecuting criminals. It involves gathering evidence, examining witnesses, and thoroughly scrutinizing the crime scenes. The investigating officials are tasked with various vital duties integral to the investigation procedures. Due to workload, police personnel may use unfair means and methods for ending investigations, securing convictions, and avoiding criticisms. The crime investigation technique requires specialized skills and training, sufficient time, appropriate forensic abilities, and facilities. This chapter examines the efficacy of police investigations and the subsequent attainment of convictions, focusing on a comparative insight into the current legal framework and the challenges under the Bharatiya Nagarik Suraksha Sanhita (BNSS) 2023. This doctrinal and non-doctrinal study applied qualitative and quantitative content analysis to evaluate the secondary data. Criminal cases experience inadequate investigation and adequate evidence. A fair investigation is essential for ensuring justice for the accused, victim, and society. If the police do not follow procedures, omitting and tampering with evidence will be detrimental by preventing the court from reviewing it. The effectiveness of police investigation significantly affects judicial verdicts. Defects in the system lead to frequent acquittals in criminal cases.