sql query case statement

i have a query and want to do the case statement in the where clause but I get the error message. Basically I want say if the type is SBW then compare to 1 otherwise comapre to whatever is in the dataabse

SELECT 

distinct U.userKey
	, U.firstName
	, U.lastName
	, S.sessionKey
	, CAST(CAST(MONTH(SU.sessionStart) AS VARCHAR) + '/' + CAST(DAY(SU.sessionStart) AS VARCHAR) + '/' + CAST(YEAR(SU.sessionStart) AS VARCHAR) AS DATETIME) AS sessionDt
	, SU.sessionStart
	, SU.sessionEnd
	, SU.sessionUnitKey
	, L.locationKey
	, L.name AS locationName
	, LPT.productTypeCode
	,LPT.title
	, CASE WHEN SU.unit IS NULL
		THEN
			LPT.description
		ELSE
			'Class ' + SU.unit
		END AS sessionType

	

		FROM users U WITH (NOLOCK)
	INNER JOIN sessionUnit SU WITH (NOLOCK) ON U.userKey = SU.instructorKey
	INNER JOIN session S WITH (NOLOCK) ON SU.sessionKey = S.sessionKey
	LEFT OUTER JOIN sessionMap SMM WITH (NOLOCK) on SMM.sessionKey = S.sessionKey
	INNER JOIN product P WITH (NOLOCK) ON S.productKey = P.productKey
	INNER JOIN lkup_productType LPT WITH (NOLOCK) ON P.productTypeKey = LPT.productTypeKey
	INNER JOIN location L WITH (NOLOCK) ON S.locationKey = L.locationKey
WHERE SU.sessionStart BETWEEN '12/1/2014' AND '12/31/2014'
AND (
        S.status = 'reserved'
        OR (
            S.status = 'enabled'
            AND (
				S.productKey != 1
				AND (
				 CASE WHEN SMM.type = 'SBW' 
					THEN 
						(
							SELECT COUNT(1)
							FROM sessionMap SM WITH (NOLOCK) 
							WHERE SM.sessionKey = S.sessionKey 
						) > = IsNull(SU.btwSeatsOverride, 1)
					ELSE 
						(
							SELECT COUNT(1)
							FROM sessionMap SM WITH (NOLOCK) 
							WHERE SM.sessionKey = S.sessionKey 
							) > = IsNull(SU.btwSeatsOverride, S.Seats)
					END 
			)) OR (S.productKey =1)

			
        )

    ) 

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