Try this:
select EMP.FIRSTNAME,
EMP.LastName, MIN(CONVERT(varchar,Eventime,14)) as TIMEIN, max(CONVERT(varchar,Eventime,14)) as TIMEOUT,
CONVERT(VARCHAR(20),DateAdd(SS,Datediff(ss,MIN(CONVERT(varchar,Eventime,14)), max(CONVERT(varchar,Eventime,14)))%(60*60*24),0),114) AS TOTALWORKTIME
from EMP inner join EVENTS on EVENTS.EMPID = EMP.ID
where EVENTS.EVENTIME between '2012-05-08 00:00:01' and '2012-05-08 12:59:59' and CONVERT(VARCHAR(20),DateAdd(SS,Datediff(ss,MIN(CONVERT(varchar,Eventime,14)), max(CONVERT(varchar,Eventime,14)))%(60*60*24),0),114)>12
group by EMP.FIRSTNAME, EMP.LASTNAME