In the context of the Negotiable Instruments Act, particularly under Section 138, it is essential for the complainant to establish the existence of a legally enforceable debt before the burden of proof shifts to the accused. This principle is clearly articulated in the judgment, which emphasizes that the complainant must prove the existence of such a debt as a prerequisite for proceeding with the case.

The judgment outlines that:

1. Legally Enforceable Debt Requirement: The court highlights that for a complaint under Section 138 to be valid, there must be a legally enforceable debt. This is a fundamental requirement that must be satisfied by the complainant [p_25].

2. Burden of Proof: The judgment specifies that the initial burden of proof lies with the complainant to demonstrate the existence of the legally enforceable debt. Only after this burden is met does it shift to the accused to prove otherwise [p_37].

3. Standard of Proof: The court discusses the differing standards of proof applicable to the complainant and the accused, reinforcing that the complainant must establish the debt beyond reasonable doubt before the accused is required to present a defense [p_40].

4. Presumptions: While the Act provides certain presumptions in favor of the holder of the cheque, these do not negate the necessity for the complainant to prove the underlying debt. The presumption under Section 139 is rebuttable and does not automatically imply the existence of a legally enforceable debt [p_28].

In summary, the requirement for a legally enforceable debt is a critical element in cases under the Negotiable Instruments Act, and the complainant must substantiate this claim before the proceedings can advance.