I don't what your trying to do in this query. As far the error is concerned this could be solution. I am sure but give a try hope it works :). Split it into two different queries.
SELECT @CRIME_DETAIL_1=count(*)
FROM t_crime_detail
where RECORD_SYNC_FROM='PS'and PS_CD=@PS_CD
and CONVERT(date, RECORD_CREATED_ON)=@REG_DT;
SELECT ( SELECT t_fir_registration.PS_CD FROM t_crime_detail INNER JOIN t_fir_registration ON t_crime_detail.FIR_REG_NUM=t_fir_registration.FIR_REG_NUM) AS PS_CD
FROM t_crime_detail
where RECORD_SYNC_FROM='PS'and PS_CD=@PS_CD
and CONVERT(date, RECORD_CREATED_ON)=@REG_DT;