So I was able to get this to work in a test project area.    Note that my STATE is different than yours, so you'll need to change that.  I tried to use the same attribute for Technical Lead as you did. 

Since you are making it a calculated value, RTC *assumes* that nobody else will change it other than the script, so that is why I get the owner and return the owner if it is not a defect or defect but not the right state.  If not, the if owner is set by someone else, it gets ignored.  I also did var's for everything so I could print things for debugging

dojo.provide("org.example.CalculatedOwner");
dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");

(function() {
dojo.declare("org.example.CalculatedOwner", null, {
   
    getValue: function(attributeId, workItem, configuration) {
        var WorkItemAttributes = com.ibm.team.workitem.api.common.WorkItemAttributes;
        var wiType = workItem.getValue(WorkItemAttributes.TYPE);
        var wiState = workItem.getValue(WorkItemAttributes.STATE);
        var wiTechLead = workItem.getValue("com.wiley.workitem.attribute.assignedBA");
        var wiOwner = workItem.getValue(WorkItemAttributes.OWNER);

    if (wiType === "defect" && wiState === "com.ibm.team.workitem.defectWorkflow.state.s1" ) {
             return wiTechLead;
    } //type = defect
    else
        return wiOwner;
    }
});
})();