Wireless Sensor Networks (WSNs) have gained a huge research interest due to their nature of deployment and widespread applicability in several applications. However, the distributed deployment nature of WSNs poses several security challenges. In this paper, an Intrusion (Outlier) detection system is proposed based on multi-strategic trust metrics, which is flexible for constantly varying WSN characterized by changes in the variations in direct trust value, recommendations and capacities. Under the multiple strategic trust metrics, this approach considered three trust metrics; they are subjective trust, witness trust and Capacity trust. Furthermore, the capacity trust is modeled as the combination of fault tolerance trust and stability trust. Each node in the network measures the overall trust of its neighbor nodes based on these three metrics and decides whether it is malicious or not. Similarly, among the available routes, one route is finalized which has more Route Trust. Extensive Simulations are conducted over the proposed intrusion detection mechanism and the performance is evaluated through Malicious Detection Rate, False Positive Rate and Packet Delivery Ratio. From the results, we have noticed that the average Malicious Detection Rats of proposed model is 93.4012% while the False Positive rate and Packet Delivery Ratio are observed as 5.5000% and 74.1745% respectively. The obtained metrics indicate that the proposed method shows an outstanding performance in Intrusions detection and packet deliveries.