## 4 Proposed Methodology
### Cluster Head Selection
#### 4.1.1 Criminal Search Optimization Algorithm (CSOA)  
The objective of this criminal search optimization algorithm (CSOA) [32] is to find the criminal by the evidence that is collected by the investigators. Cooperative jamming and power randomness are used to improve covertness performance [33]. To achieve the goal of CSOA, the entire process is segmented into four phases. These phases are explained below:  
Phase 1: Initialization  
This initialization process is carried out in this phase. Here the parameters, SI (sub-investigators), and the undercover officers are initialized that are being used by the CSOA. At first, all informants and SIs are obtaining suspects' random information at their pre-defined search location. The parameters such as \(inq_{\mathrm{max}}\) and \(Random_{\mathrm{max}}\) represent maximum inquiries and the random numbers' maximum limit, respectively. Phase 2: Evaluating the Performance and Searching for the CriminalThe chief investigator (CI) collects all the information that is gathered by the informer and SI and creates the evidence against the accused person by using the objective function. Initially (\(s=0\)), the defender is considered as primary suspect based on best fitness (evidence) as shown by below equation. \[P^{s}=B[S\!I^{s^{*}},In^{s^{*}}] \tag{3}\]  
The terms \(P^{s}\) is the primary suspects' information that is available in CI; \(B\) represents the best, \(SI^{s^{*}}\) represents the accused persons' best information available with the \(SI\); and \(In^{s^{*}}\) represents the accused persons' best information available with the informers; then \(s\) is for investigation steps. In the following phases (\(s\
eq 0\)), the comparison is made between the primary accused persons' present inquiry stage and previous inquiry stage to select the evidence of the present primary accused person by using Equation (4),  
\[BInfo^{s}=\left\{ \begin{array}{rl}pr_{AP}^{is}&\text{if }e(pr_{AP}^{is})<e(pr_{AP}^{is-1})\\ pr_{AP}^{is-1}&else if\ e(pr_{AP}^{is})\geq e(pr_{AP}^{is-1})\end{array} \right. \tag{4}\]  
In the above equation, the term \(BInfo^{s}\) represents the accused persons' best information that is present with the CI; the term \(pr_{AP}^{is-1}\) signifies the best prior information of the primary accused person with the CI; the terms \(e(pr_{AP}^{is})\) and \(e(pr_{AP}^{is-1})\) represents the evidence after processing \(pr_{AP}^{is}\) and \(pr_{AP}^{is-1}\) information, respectively; in the beginning, viz. when \(s=0\), \(pr_{AP}^{is}\) is considered as \(BInfo^{s}\). Phase 3: Update Information  
The updating of information is carried out in three steps. They are:  
_Interrogation_--The accused persons' information with the investigator is upgraded using Equation (5). \[BInfo^{s+1}=BInfo^{s}+BInfo^{s}\times R^{s} \tag{5}\]  
From the above equation, the term \(BInfo^{s+1}\) represent the primary accused persons' updated information; the term \(BInfo^{s}\) represents the primary accused persons' present information which is available with CI; \(R^{s}\) is the random number with the range [\(-1\), \(1\)]. The term \(s\) is the investigation stages. _Information Updating of SI_--The information from \(SI\) is upgraded by using Equation (6) in this step. \[SI^{s+1}=SI^{s}+d_{1}\times SI_{BInfo}^{s}+x\times d_{2}\times SI_{y}^{s}+(1- x)\times d_{3}\times SI_{d}^{s} \tag{6}\]  
The term \(SI^{s}\) is the primary suspects' present information that is available in \(SI\); the term \(SI^{s+1}\) is the primary suspects' updated information that is available in \(SI\); the evidence gathered from the primary accused person by the \(SI\) is represented as \(SI_{BInfo}^{s}\) and is given as (\(BInfo^{s}-SI^{s}\)). The evidence gathered from previous best evidence by \(SI\) is given as (\(SI_{BInfo}^{s-1}-SI^{s}\)) is represented by \(SI_{y}^{s}\). The evidence collected from random \(SI\) is given as (\(SI_{d}^{s}-SI^{s}\)) is represented by \(SI_{d}^{s}\).