Strange SQL Query Issue

I am querying my company's Atlassian JIRA tracking system and reporting on trouble tickets by status assigned to the username "tristanboughton." I have tried writing and re-writing the query multiple times and get one of two results: (1) all tickets (regardless of whether or not they were originally) are displayed as assigned to "tristanboughton" or (2) all tickets, despite filters applied to only display issues assigned to "tristanboughton," are displayed, including ones assigned to other users.

What am I missing?

SELECT     CASE PROJECT WHEN '10180' THEN 'Corporate Applications' WHEN '10160' THEN 'Corporate Reporting' WHEN '10182' THEN 'CMMI' WHEN '10100' THEN
                       'Information Technology Office' WHEN '10230' THEN 'Domain Controller/Migration' END AS ProjectName, REPORTER, ASSIGNEE, 
                      CASE issuetype WHEN '1' THEN 'Product Defect' WHEN '3' THEN 'Task' WHEN '4' THEN 'Risk' WHEN '20' THEN 'Report' WHEN '21' THEN 'Change' WHEN
                       '22' THEN 'Customization' WHEN '23' THEN 'Updated' WHEN '24' THEN 'Research' WHEN '25' THEN 'Applications Issue Type' WHEN '26' THEN 'Enhancement'
                       END AS IssueTypeDef, SUMMARY, DESCRIPTION, 
                      CASE PRIORITY WHEN '1' THEN 'Very High' WHEN '2' THEN 'High' WHEN '3' THEN 'Moderate' WHEN '4' THEN 'Low' WHEN '5' THEN 'Very Low' END AS
                       IssuePriority, PRIORITY, 
                      CASE issuestatus WHEN '1' THEN 'Open' WHEN '3' THEN 'In Progress' WHEN '4' THEN 'Reopened' WHEN '5' THEN 'Resolved' WHEN '6' THEN 'Closed'
                       END AS IssueStatusName, CREATED, UPDATED, DUEDATE, ID, PROJECT, TIMESPENT, issuetype, issuestatus
FROM         jiraissue
WHERE     (PROJECT = '10180') AND (ASSIGNEE = 'tristanboughton') OR
                      (PROJECT = '10160') AND (ASSIGNEE = 'tristanboughton') OR
                      (PROJECT = '10182') AND (ASSIGNEE = 'tristanboughton') OR
                      (PROJECT = '10100') AND (ASSIGNEE = 'tristanboughton') OR
                      (PROJECT = '10230') AND (issuetype <> '12') AND (issuestatus IN (@StatusParameter)) AND (ASSIGNEE = 'tristanboughton')
ORDER BY ProjectName, PRIORITY

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