A bounded domain has been defined by the Einthoven axes over thorax in the frontal plane. Using spin harmonic generator matrix model criteria have been found for locating points of null (or minimum) ECG potential with respect to WCT. The locus of these null points may be termed as neutral axis. The monopolar ECG has been mapped at about 45 points on the frontal surface of thorax bounded by Einthoven axes. The Autocad version.10 package has been used for creation of sampled value database from ECG records. The time plane as well as spin harmonic frequency planes have been used to map the neutral axis locus. A preliminary selective criterion of probability greater than 0.5 has been used for selection of ECG records to test neutrality property. The observation suggests that locus of neutral points intersect the RA-LA axis at a location between the Suprasternal notch and left arm and the RA-LL axis at a point 6-12mm below RA-LA axis.