Based on the provided legal document, here are the key points regarding the case Director, Central Bureau of Investigation & Anr. versus Shri D.P. Singh:

• Case Citation and Details: The case is Civil Appeal No. 1485 of 2003, decided by the Supreme Court of India on 16-12-2009, involving the Director, CBI as the Appellant and Shri D.P. Singh as the Respondent. (!) (!)
• Subject Matter: The core issue concerns Employment Law, specifically Seniority calculations under the Service Law, particularly the Special Police Establishment (Executive Staff) Recruitment Rules, 1963. (!) (!)
• Factual Background: The Respondent joined the U.P. Police Service as a Sub-Inspector in 1964 and was sent on deputation to the CBI in 1966. While on deputation, he was appointed to the post of Inspector in 1970 and then appointed to the post of Deputy Superintendent of Police (Dy.S.P.) on an ad-hoc/officiating basis on November 24, 1977. (!) (!) (!)
• Absorption and Dispute: Although the Respondent exercised his option for absorption in 1980 and the request was accepted in 1983, the formal absorption order was only issued on May 15, 1995, with effect from June 29, 1987. The Respondent claimed seniority in the grade of Dy.S.P. from November 24, 1977, whereas the authorities counted it from the date of absorption, June 29, 1987. (!) (!)
• Lower Court Proceedings: The Central Administrative Tribunal (CAT) dismissed the Respondent's original application and review application. The High Court of Delhi allowed a writ petition filed by the Respondent, directing that his seniority be counted from November 24, 1977. (!) (!)
• Legal Provision Involved: The primary legal instrument under consideration is the Office Memorandum dated May 29, 1986, issued by the Department of Personnel and Training (DOPT), specifically sub-para (iv) of para 7 regarding the seniority of persons absorbed after being on deputation. (!) (!) (!)
• Content of the Office Memorandum: The Memorandum states that normally, seniority for a deputationist absorbed later is counted from the date of absorption. However, if the officer was already holding the same or equivalent grade on a regular basis in their parent department on the date of absorption, seniority may be counted from the date of deputation to that grade or the date of regular appointment in the parent department, whichever is later. (!) (!) (!)
• Applicability to the Case: The Court held that the exception in the Memorandum does not apply because the Respondent was not holding the post of Dy.S.P. or an equivalent grade on a regular basis in his parent department (U.P. Police) at the time of his absorption. His appointment in CBI was purely ad-hoc/officiating. (!) (!) (!)
• Statutory Construction Principle: The Court emphasized that it is not a sound principle of construction to treat words in a statute as surplussage if they can have appropriate application. The first part of sub-para (iv) ("normally be counted from the date of absorption") must be given effect, distinguishing it from cases where the officer holds the grade regularly in the parent department. (!)
• Precedents: The Court distinguished the case from K. Madhavan and Another v. Union of India, noting that while service is not wiped out by transfer, the principle applies only if the officer held the specific grade regularly in the parent department, which was not the case here. (!) (!)
• Tribunal's Finding: The Tribunal correctly observed that as long as the applicant could claim no lien on the post of Dy.S.P. in CBI, he could not claim seniority there; the earlier lien with U.P. Police ceased upon absorption. (!)
• Judgment: The Supreme Court allowed the appeal, set aside the judgment of the High Court, and held that the Respondent's seniority in the grade of Dy.S.P. must be counted from the date of absorption, i.e., June 29, 1987. (!) (!)