The performance of laminated composite structures is compromised by the presence of defects such as delamination, which greatly reduces its ability to support load. A delamination, being an interior defect, is not easily identified. Damage detection, including delamination identification, is an inverse problem. It is important to characterize the effect of damage in the structure prior to developing a robust detection procedure. Therefore, it is important to use an accurate and efficient analysis procedure in damage characterization studies. In recent years, there has been an increase in the use of damage indices, many of which make use of mode shapes as damage locators. A damage index, based on inplane modal strains, was introduced by Chattopadhyay and Dragomir to characterize the location and severity of delamination in composite and smart composite structures. In this paper, this damage index is further modified to include a combination of inplane and out of plane modal strains associated with multiple vibratory modes. Composite laminates, of arbitrary thickness, with multiple, discrete delaminations at various ply interfaces are considered. Comparisons are made with corresponding healthy laminates. The performance of the damage index is compared numerically with results using other damage indices, such as Modal Strain Assurance Criterion (MSAC) and the Coordinate Modal Strain Assurance Criterion (COMSAC). Experiments are conducted to verify the accuracy of me damage indices using a Laser Scanning Vibrometer. The analysis is conducted using a newly developed layer wise theory. The theory provides accurate ply level stress information, which is essential in understanding the kinematics of delamination. The presence of multiple discrete delaminations is modeled using Heavyiside step functions.