I think this is much cleaner solution:
SELECT
-- 17530101 or 1753-01-01 is the minimum date in SQL Server
DATEADD(dd, ((DATEDIFF(dd, '17530101', GETDATE()) / 7) * 7) - 7, '17530101') AS [LowerLimit], -- Last Week's Monday
DATEADD(dd, ((DATEDIFF(dd, '17530101', GETDATE()) / 7) * 7) - 1, '17530101') AS [UpperLimit] -- Last Week's Sunday.
Which can be used like this in a real world query:
SELECT
*
FROM
SomeTable
WHERE
SomeTable.[Date] >= DATEADD(dd, ((DATEDIFF(dd, '17530101', GETDATE()) / 7) * 7) - 7, '17530101') AND
SomeTable.[Date] <= DATEADD(dd, ((DATEDIFF(dd, '17530101', GETDATE()) / 7) * 7) - 1, '17530101')
Here are some tests:
1. Leap Year
Current Date: 2016-02-29 00:00:00.000
Results:
LowerLimit UpperLimit
2016-02-22 00:00:00.000 2016-02-28 00:00:00.000
2. Last Week was in different year
Current Date: 2016-01-06 00:00:00.000
LowerLimit UpperLimit
2015-12-28 00:00:00.000 2016-01-03 00:00:00.000
3. Lower limit in previous month and upper limit in current month
Current Date: 2016-05-04 00:00:00.000
LowerLimit UpperLimit
2016-04-25 00:00:00.000 2016-05-01 00:00:00.000
4. Current Date is Sunday
Current Date: 2016-05-08 00:00:00.000
LowerLimit UpperLimit
2016-04-25 00:00:00.000 2016-05-01 00:00:00.000