This thesis discusses through analysis and explanation suspect's rights and interrogation which are deemed the most significant and critical procedure in the initial investigation as it establishes the truth through pointing out the link between the suspect to the crime in the light that the suspect's rights are safeguarded his guarantees and conditions stipulated by the law are taken into consideration. The thesis shows that interrogating a suspect has a dual function nature, in comparison with other procedures. It assists the interrogator collecting pieces of evidence to prove the accusation against the suspect. Also, it is a means of defense for the suspect to submit his/her arguments in defense. In addition, this thesis points out that the Omani Penal Code gives a high attention to the subject of interrogating suspects as it provides a number of protections to safeguard his rights; therefore, the suspect have full freedom to give his statements and defend himself with all means of defense provided for by the law. Also, the thesis states that infringement of rights related to interrogation may result in nullity which could either be "absolute" ensuing from violating the rules of the intrinsic procedures related the public order stipulated by article (209) of the criminal procedures or relative ensuing from failure to comply with the provisions of the procedures that are related to the interest of the litigants but not to the public order according to article (210). The thesis addresses these two types of nullity and their related provisions. The thesis proposes a number of recommendations as following: • To Introduce a new article in the Criminal Procedures Code stipulating the following: (The public prosecutor, in case of commissioning law enforcement officer, shall determine the requirements to be met and the procedures to be undertaken. The law enforcement officer may interrogate the suspect if s/he fears running out of time should this be related to the work assigned to him/her as deemed necessary for uncovering the truth. • To designate imperatively a lawyer for every suspect charged with felony or at least a felony whose sentence is capital punishment or life imprisonment during initial investigation and trial. • To Introduce new article to the criminal procedures stipulating the following: (The public prosecution member shall notify the defendant's lawyer with the date of interrogation in a prior suitable time in order to be able to present before the court or interrogation). To revoke article (3) of the Public Prosecution Law as it conflicts article (64/1) of the Basic Statue of the State which solely entrusts the public prosecution with task of investigations and handling of all criminal cases whatsoever